diff --git a/prism/src/userinterface/simulator/GUISimulator.java b/prism/src/userinterface/simulator/GUISimulator.java
index 2c55d43f..1ce269b6 100644
--- a/prism/src/userinterface/simulator/GUISimulator.java
+++ b/prism/src/userinterface/simulator/GUISimulator.java
@@ -520,10 +520,20 @@ public class GUISimulator extends GUIPlugin implements MouseListener, ListSelect
 
 			setComputing(true);
 
-			if (isOldUpdate()) {
-				engine.computeTransitionsForCurrentState();
+			try {
+				if (isOldUpdate()) {
+					engine.computeTransitionsForCurrentState();
+				}
+				engine.automaticTransitions(noSteps, displayPathLoops);
+			} catch (PrismException e) {
+				this.error(e.getMessage());
+				guiMultiModel.getHandler().modelParseFailed(e, false);
+				guiMultiModel.tabToFront();
+
+				// Even if there was an exception, we continue and try
+				// to update the path display, as there may be intermediate steps
+				// that have succeeded
 			}
-			engine.automaticTransitions(noSteps, displayPathLoops);
 
 			// Update model/path/tables/lists
 			pathTableModel.updatePathTable();
@@ -534,12 +544,12 @@ public class GUISimulator extends GUIPlugin implements MouseListener, ListSelect
 			// Update display
 			repaintLists();
 			updatePathInfo();
-			setComputing(false);
-
 		} catch (PrismException e) {
 			this.error(e.getMessage());
-			guiMultiModel.getHandler().modelParseFailed((PrismLangException) e, false);
+			guiMultiModel.getHandler().modelParseFailed(e, false);
 			guiMultiModel.tabToFront();
+		} finally {
+			setComputing(false);
 		}
 	}
 
@@ -556,10 +566,22 @@ public class GUISimulator extends GUIPlugin implements MouseListener, ListSelect
 			}
 
 			setComputing(true);
-			if (isOldUpdate()) {
-				engine.computeTransitionsForCurrentState();
+
+			try {
+				if (isOldUpdate()) {
+					engine.computeTransitionsForCurrentState();
+				}
+				engine.automaticTransitions(time, displayPathLoops);
+			} catch (PrismException e) {
+				this.error(e.getMessage());
+				guiMultiModel.getHandler().modelParseFailed(e, false);
+				guiMultiModel.tabToFront();
+
+				// Even if there was an exception, we continue and try
+				// to update the path display, as there may be intermediate steps
+				// that have succeeded
 			}
-			engine.automaticTransitions(time, displayPathLoops);
+
 			// Update model/path/tables/lists
 			pathTableModel.updatePathTable();
 			int height = (int) pathTable.getPreferredSize().getHeight();
@@ -569,11 +591,13 @@ public class GUISimulator extends GUIPlugin implements MouseListener, ListSelect
 			// Update display
 			repaintLists();
 			updatePathInfo();
-			setComputing(false);
 
 		} catch (PrismException e) {
 			this.error(e.getMessage());
 		}
+		finally {
+			setComputing(false);
+		}
 	}
 
 	/** Backtrack to a certain time. */
@@ -588,9 +612,10 @@ public class GUISimulator extends GUIPlugin implements MouseListener, ListSelect
 			// Update display
 			repaintLists();
 			updatePathInfo();
-			setComputing(false);
 		} catch (PrismException e) {
 			this.error(e.getMessage());
+		} finally {
+			setComputing(false);
 		}
 	}
 
@@ -606,9 +631,10 @@ public class GUISimulator extends GUIPlugin implements MouseListener, ListSelect
 			// Update display
 			repaintLists();
 			updatePathInfo();
-			setComputing(false);
 		} catch (PrismException e) {
 			this.error(e.getMessage());
+		} finally {
+			setComputing(false);
 		}
 	}
 
@@ -624,24 +650,28 @@ public class GUISimulator extends GUIPlugin implements MouseListener, ListSelect
 			// Update display
 			repaintLists();
 			updatePathInfo();
-			setComputing(false);
 		} catch (PrismException e) {
 			this.error(e.getMessage());
+		} finally {
+			setComputing(false);
 		}
 	}
 
 	/** Remove the prefix of the current path up to the given path step. */
 	public void a_removePreceding(int step) throws PrismException
 	{
-		setComputing(true);
-		engine.removePrecedingStates(step);
-		// Update model/path/tables/lists
-		pathTableModel.updatePathTable();
-		updateTableModel.updateUpdatesTable();
-		// Update display
-		repaintLists();
-		updatePathInfo();
-		setComputing(false);
+		try {
+			setComputing(true);
+			engine.removePrecedingStates(step);
+			// Update model/path/tables/lists
+			pathTableModel.updatePathTable();
+			updateTableModel.updateUpdatesTable();
+			// Update display
+			repaintLists();
+			updatePathInfo();
+		} finally {
+			setComputing(false);
+		}
 	}
 
 	public void a_manualUpdate()
@@ -681,13 +711,12 @@ public class GUISimulator extends GUIPlugin implements MouseListener, ListSelect
 			// Update display
 			repaintLists();
 			updatePathInfo();
-			setComputing(false);
 
 		} catch (NumberFormatException e) {
 			this.error("The Auto update \'no. steps\' parameter is invalid.\nIt must be a positive integer representing a step in the path table");
-			setComputing(false);
 		} catch (PrismException e) {
 			this.error(e.getMessage());
+		} finally {
 			setComputing(false);
 		}
 	}
@@ -736,9 +765,10 @@ public class GUISimulator extends GUIPlugin implements MouseListener, ListSelect
 				return;
 			setComputing(true);
 			engine.exportPath(getChooserFile());
-			setComputing(false);
 		} catch (PrismException e) {
 			error(e.getMessage());
+		} finally {
+			setComputing(false);
 		}
 	}
 
@@ -750,9 +780,10 @@ public class GUISimulator extends GUIPlugin implements MouseListener, ListSelect
 			Graph graphModel = new Graph();
 			guiProp.getGraphHandler().addGraph(graphModel);
 			engine.plotPath(graphModel);
-			setComputing(false);
 		} catch (PrismException e) {
 			error(e.getMessage());
+		} finally {
+			setComputing(false);
 		}
 	}
 
@@ -817,7 +848,6 @@ public class GUISimulator extends GUIPlugin implements MouseListener, ListSelect
 			getPrism().getMainLog().resetNumberOfWarnings();
 			parser.State initialStateObject = initialState == null ? null : new parser.State(initialState, parsedModel);
 			new SimPathPlotThread(this, engine, parsedModel, initialStateObject, simPathDetails, maxPathLength, graphModel).start();
-			setComputing(false);
 
 			// store initial state for next time
 			lastInitialState = initialState;
@@ -828,6 +858,8 @@ public class GUISimulator extends GUIPlugin implements MouseListener, ListSelect
 				guiMultiModel.getHandler().modelParseFailed((PrismLangException) e, false);
 				guiMultiModel.tabToFront();
 			}
+		} finally {
+			setComputing(false);
 		}
 	}