diff --git a/swing/src/net/sf/openrocket/gui/widgets/SaveFileChooser.java b/swing/src/net/sf/openrocket/gui/widgets/SaveFileChooser.java
index a501e66c9..61b5ce3ba 100644
--- a/swing/src/net/sf/openrocket/gui/widgets/SaveFileChooser.java
+++ b/swing/src/net/sf/openrocket/gui/widgets/SaveFileChooser.java
@@ -6,6 +6,8 @@ import net.sf.openrocket.startup.Application;
 import javax.swing.JFileChooser;
 import javax.swing.JOptionPane;
 import java.io.File;
+import java.util.regex.Pattern;
+import java.util.regex.PatternSyntaxException;
 
 public class SaveFileChooser extends JFileChooser {
     private static final Translator trans = Application.getTranslator();
@@ -20,55 +22,79 @@ public class SaveFileChooser extends JFileChooser {
     @Override
     public void setSelectedFile(File file) {
         currentFile = file;
-        if (file != null) {
-            if (file.getParentFile() != getCurrentDirectory()) {
-                cwd = getCurrentDirectory();
-                fileName = getFilenameInput(file);
+        if (file == null) {
+            super.setSelectedFile(null);
+            return;
+        }
+
+        if (file.getParentFile() != getCurrentDirectory()) {
+            cwd = getCurrentDirectory();
+            fileName = getFilenameInput(currentFile, cwd);
+            if (getIllegalChar(fileName) != null) {
                 return;
-            } else {
-                fileName = file.getName();
             }
         }
+
         super.setSelectedFile(file);
+        fileName = file.getName();
+        cwd = getCurrentDirectory();
     }
 
     @Override
     public void approveSelection() {
-        if (!containsIllegalChars(fileName)) {
+        Character c = getIllegalChar(fileName);
+        if (c != null) {
+            // Illegal character found
+            JOptionPane.showMessageDialog(getParent(),
+                    String.format(trans.get("SaveAsFileChooser.illegalFilename.message"), fileName, c),
+                    trans.get("SaveAsFileChooser.illegalFilename.title"),
+                    JOptionPane.WARNING_MESSAGE);
+        } else {
+            // Successful filename
             super.setSelectedFile(currentFile);
             setCurrentDirectory(cwd);
             super.approveSelection();
         }
     }
 
-    private boolean containsIllegalChars(String filename) {
+    /**
+     * Returns an illegal character if one is found in the filename, otherwise returns null.
+     * @param filename The filename to check
+     * @return The illegal character, or null if none is found
+     */
+    private Character getIllegalChar(String filename) {
         if (filename == null || filename.isEmpty()) {
-            return false;
+            return null;
         }
         for (char c : ILLEGAL_CHARS) {
             if (filename.indexOf(c) >= 0) {
-                // Illegal character found
-                JOptionPane.showMessageDialog(getParent(),
-                        String.format(trans.get("SaveAsFileChooser.illegalFilename.message"), filename, c),
-                        trans.get("SaveAsFileChooser.illegalFilename.title"),
-                        JOptionPane.WARNING_MESSAGE);
-                return true;
+                return c;
             }
         }
-        return false;
+        return null;
     }
 
-    private String getFilenameInput(File file) {
-        if (file == null) {
+    /**
+     * Returns the filename input by the user, or null if the filename is invalid.
+     * You can't simply use getSelectedFile().getName() because it won't work for malformed filenames.
+     * @param file The file to get the filename from
+     * @param cwd The current working directory
+     * @return The filename input by the user, or null if the filename is invalid
+     */
+    private String getFilenameInput(File file, File cwd) {
+        if (file == null || cwd == null) {
             return null;
         }
 
         String fullPath = file.getAbsolutePath();
         String cwdPath = cwd.getAbsolutePath();
 
-        String relativePath = fullPath.replaceFirst("^" + cwdPath, "").trim();
-        relativePath = relativePath.replaceFirst("^" + File.separator, "");
-
-        return relativePath;
+        try {
+            String relativePath = fullPath.replaceFirst(Pattern.quote(cwdPath), "").trim();
+            relativePath = relativePath.replaceFirst(Pattern.quote(File.separator), "");
+            return relativePath;
+        } catch (PatternSyntaxException e) {
+            return null;
+        }
     }
 }