I am using Office 2000 on Windows XP and noticed some peculiar behaviour.
When I use CPU intensive VB-code with Excel, something (I think Windows XP; I
am not sure) will spawn an extra thread for Excel. In the taskmanager I can
see I get extra instances for my Excel stuff.

This however causes some kind of loop, so that Excel never finishes the code.

This is also not 100% predictable: the same code will sometimes execute
succesfully and sometimes will spawn an extra thread and loop indefinitly.