Error when starting Josm

[abbst@…]

What steps will reproduce the problem?

1. Starting Josm
2. Open GPX file
3. Plugin "Buildings_tools" seemed to be making the error!? When deinstalled, Josm is running.

What is the expected result?

What happens instead?

Please provide any additional information below. Attach a screenshot if
possible.

Repository Root: http://josm.openstreetmap.de/svn
Build-Date: 2011-03-09 12:21:24
Last Changed Author: Upliner
Revision: 3966
Repository UUID: 0c6e7542-c601-0410-84e7-c038aed88b3b
URL: http://josm.openstreetmap.de/svn/trunk
Last Changed Date: 2011-03-09 11:48:50 +0100 (Wed, 09 Mar 2011)
Last Changed Rev: 3966

Identification: JOSM/1.5 (3966 de)
Memory Usage: 80 MB / 506 MB (42 MB allocated, but free)
Java version: 1.6.0_15, Apple Inc., Java HotSpot(TM) 64-Bit Server VM
Operating system: Mac OS X

Plugin: PicLayer (24308)
Plugin: buildings_tools (23804)
Plugin: openstreetbugs (23747)
Plugin: pdfimport (24186)
Plugin: walkingpapers (22549)

java.lang.IncompatibleClassChangeError: Expecting non-static method converttomultipoly.MultipolyAction.getCurrentDataSet()Lorg/openstreetmap/josm/data/osm/DataSet;
	at converttomultipoly.MultipolyAction.updateEnabledState(MultipolyAction.java:125)
	at org.openstreetmap.josm.actions.JosmAction$LayerChangeAdapter.layerAdded(JosmAction.java:201)
	at org.openstreetmap.josm.gui.MapView.fireLayerAdded(MapView.java:146)
	at org.openstreetmap.josm.gui.MapView.addLayer(MapView.java:281)
	at org.openstreetmap.josm.Main.addLayer(Main.java:267)
	at org.openstreetmap.josm.io.GpxImporter$1.run(GpxImporter.java:49)
	at java.awt.event.InvocationEvent.dispatch(InvocationEvent.java:209)
	at java.awt.EventQueue.dispatchEvent(EventQueue.java:633)
	at java.awt.EventDispatchThread.pumpOneEventForFilters(EventDispatchThread.java:296)
	at java.awt.EventDispatchThread.pumpEventsForFilter(EventDispatchThread.java:211)
	at java.awt.EventDispatchThread.pumpEventsForFilter(EventDispatchThread.java:205)
	at java.awt.Dialog$1.run(Dialog.java:1045)
	at java.awt.Dialog$3.run(Dialog.java:1097)
	at java.security.AccessController.doPrivileged(Native Method)
	at java.awt.Dialog.show(Dialog.java:1095)
	at java.awt.Component.show(Component.java:1563)
	at java.awt.Component.setVisible(Component.java:1515)
	at java.awt.Window.setVisible(Window.java:841)
	at java.awt.Dialog.setVisible(Dialog.java:985)
	at org.openstreetmap.josm.gui.progress.PleaseWaitProgressMonitor$3.run(PleaseWaitProgressMonitor.java:83)
	at java.awt.event.InvocationEvent.dispatch(InvocationEvent.java:209)
	at java.awt.EventQueue.dispatchEvent(EventQueue.java:633)
	at java.awt.EventDispatchThread.pumpOneEventForFilters(EventDispatchThread.java:296)
	at java.awt.EventDispatchThread.pumpEventsForFilter(EventDispatchThread.java:211)
	at java.awt.EventDispatchThread.pumpEventsForHierarchy(EventDispatchThread.java:201)
	at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:196)
	at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:188)
	at java.awt.EventDispatchThread.run(EventDispatchThread.java:12

[bastiK]

This looks, like you got wrong plugin version. Please reopen, if this happens after update of both josm and plugins.