I was wondering what was causing my copy of CityDesk to crash. Now I know. Thanks to the folks at Fog Creek Software for pointing out the source of the bug and the workaround until Microsoft offers a fix.

This bug appears to be caused by Microsoft KB891781. We have found numerous other products on the web that have the same problem since this hotfix was released by Microsoft.

We are awaiting a reply from Microsoft on what appears to be a quite severe bug that they introduced with this "hotfix." We have spoken to Microsoft and they confirm that they can reproduce the bug.