diff --git a/core/resources/l10n/messages.properties b/core/resources/l10n/messages.properties
index ebe011ef2..7da962ad7 100644
--- a/core/resources/l10n/messages.properties
+++ b/core/resources/l10n/messages.properties
@@ -571,9 +571,11 @@ SimuRunDlg.lbl.Altitude = Altitude:
 SimuRunDlg.lbl.Velocity = Velocity:
 SimuRunDlg.msg.Unabletosim = Unable to simulate:
 SimuRunDlg.msg.errorOccurred = An error occurred during the simulation:
+SimuRunDlg.msg.branchErrorOccurred = An error occurred during simulation branch
 
 BasicEventSimulationEngine.error.noMotorsDefined = No motors defined in the simulation.
-BasicEventSimulationEngine.error.cantCalculateStability = Can't calculate rocket stability.
+BasicEventSimulationEngine.error.activeLengthZero = Active airframe has length 0
+BasicEventSimulationEngine.error.cantCalculateStability = Can't calculate stability
 BasicEventSimulationEngine.error.earlyMotorBurnout = Motor burnout without liftoff.
 BasicEventSimulationEngine.error.noConfiguredIgnition = No motors configured to ignite at liftoff
 BasicEventSimulationEngine.error.noIgnition = No motors ignited.
diff --git a/core/src/net/sf/openrocket/simulation/BasicEventSimulationEngine.java b/core/src/net/sf/openrocket/simulation/BasicEventSimulationEngine.java
index c903addbf..2e8212936 100644
--- a/core/src/net/sf/openrocket/simulation/BasicEventSimulationEngine.java
+++ b/core/src/net/sf/openrocket/simulation/BasicEventSimulationEngine.java
@@ -86,13 +86,6 @@ public class BasicEventSimulationEngine implements SimulationEngine {
 			throw new MotorIgnitionException(trans.get("BasicEventSimulationEngine.error.noMotorsDefined"));
 		}
 
-		// Can't calculate stability
-		if (currentStatus.getSimulationConditions().getAerodynamicCalculator()
-			.getCP(currentStatus.getConfiguration(),
-				   new FlightConditions(currentStatus.getConfiguration()),
-				   new WarningSet()).weight < MathUtil.EPSILON)
-			throw new SimulationException(trans.get("BasicEventSimulationEngine.error.cantCalculateStability"));
-
 		// Problems that let us simulate, but result is likely bad
 			
 		// No recovery device
@@ -157,6 +150,8 @@ public class BasicEventSimulationEngine implements SimulationEngine {
 		Coordinate originVelocity = currentStatus.getRocketVelocity();
 		
 		try {
+
+			checkGeometry(currentStatus);
 			
 			// Start the simulation
 			while (handleEvents()) {
@@ -284,6 +279,7 @@ public class BasicEventSimulationEngine implements SimulationEngine {
 			flightData.getWarningSet().addAll(currentStatus.getWarnings());
 
 			e.setFlightData(flightData);
+			e.setFlightDataBranch(currentStatus.getFlightData());
 			
 			throw e;
 		}
@@ -504,6 +500,10 @@ public class BasicEventSimulationEngine implements SimulationEngine {
 					boosterStatus.getConfiguration().clearStagesAbove(stageNumber);
 					
 					toSimulate.push(boosterStatus);
+
+					// Make sure upper stages can still be simulated
+					checkGeometry(currentStatus);
+					
 					log.info(String.format("==>> @ %g; from Branch: %s ---- Branching: %s ---- \n",
 										   currentStatus.getSimulationTime(), 
 										   currentStatus.getFlightData().getBranchName(), boosterStatus.getFlightData().getBranchName()));
@@ -665,8 +665,24 @@ public class BasicEventSimulationEngine implements SimulationEngine {
 			return null;
 		}
 	}
-	
-	
+
+	// we need to check geometry to make sure we can simulation the active
+	// stages in a simulation branch when the branch starts executing, and
+	// whenever a stage separation occurs
+	private void checkGeometry(SimulationStatus currentStatus) throws SimulationException {
+		
+		// Active stages have total length of 0.
+		if (currentStatus.getConfiguration().getLengthAerodynamic() < MathUtil.EPSILON) {
+			throw new SimulationException(trans.get("BasicEventSimulationEngine.error.activeLengthZero"));
+		}
+		
+		// Can't calculate stability
+		if (currentStatus.getSimulationConditions().getAerodynamicCalculator()
+			.getCP(currentStatus.getConfiguration(),
+				   new FlightConditions(currentStatus.getConfiguration()),
+				   new WarningSet()).weight < MathUtil.EPSILON)
+			throw new SimulationException(trans.get("BasicEventSimulationEngine.error.cantCalculateStability"));
+	}
 	
 	private void checkNaN() throws SimulationException {
 		double d = 0;
diff --git a/core/src/net/sf/openrocket/simulation/exception/SimulationException.java b/core/src/net/sf/openrocket/simulation/exception/SimulationException.java
index e0e8ee8ec..720eadce0 100644
--- a/core/src/net/sf/openrocket/simulation/exception/SimulationException.java
+++ b/core/src/net/sf/openrocket/simulation/exception/SimulationException.java
@@ -1,10 +1,12 @@
 package net.sf.openrocket.simulation.exception;
 
 import net.sf.openrocket.simulation.FlightData;
+import net.sf.openrocket.simulation.FlightDataBranch;
 	
 public class SimulationException extends Exception {
 
 	private FlightData flightData = null;
+	private FlightDataBranch flightDataBranch = null;
 	
 	public SimulationException() {
 
@@ -29,4 +31,13 @@ public class SimulationException extends Exception {
 	public FlightData getFlightData() {
 		return flightData;
 	}
+
+	public void setFlightDataBranch(FlightDataBranch f) {
+		flightDataBranch = f;
+	}
+
+	public FlightDataBranch getFlightDataBranch() {
+		return flightDataBranch;
+	}
+
 }
diff --git a/swing/src/net/sf/openrocket/gui/simulation/SimulationRunDialog.java b/swing/src/net/sf/openrocket/gui/simulation/SimulationRunDialog.java
index 63ac79c29..2ff3c7101 100644
--- a/swing/src/net/sf/openrocket/gui/simulation/SimulationRunDialog.java
+++ b/swing/src/net/sf/openrocket/gui/simulation/SimulationRunDialog.java
@@ -38,6 +38,7 @@ import net.sf.openrocket.l10n.Translator;
 import net.sf.openrocket.motor.IgnitionEvent;
 import net.sf.openrocket.motor.MotorConfiguration;
 import net.sf.openrocket.rocketcomponent.FlightConfiguration;
+import net.sf.openrocket.simulation.FlightDataBranch;
 import net.sf.openrocket.simulation.FlightEvent;
 import net.sf.openrocket.simulation.SimulationStatus;
 import net.sf.openrocket.simulation.customexpression.CustomExpression;
@@ -433,12 +434,20 @@ public class SimulationRunDialog extends JDialog {
 						null, simulation.getName(), JOptionPane.ERROR_MESSAGE);
 
 			} else if (t instanceof SimulationException) {
+				String title = simulation.getName();
+				FlightDataBranch dataBranch = ((SimulationException) t).getFlightDataBranch();
 
+				String message;
+				if (dataBranch != null) {
+					message = trans.get("SimuRunDlg.msg.branchErrorOccurred") + "\"" + dataBranch.getBranchName() + "\"";
+				} else {
+					message = trans.get("SimuRunDlg.msg.errorOccurred");
+				}
 				DetailDialog.showDetailedMessageDialog(SimulationRunDialog.this,
 						new Object[] {
 								//// A error occurred during the simulation:
-								trans.get("SimuRunDlg.msg.errorOccurred"), t.getMessage() },
-						null, simulation.getName(), JOptionPane.ERROR_MESSAGE);
+								message, t.getMessage() },
+													   null, simulation.getName(), JOptionPane.ERROR_MESSAGE);
 
 			} else {