In hardy a C# application I made myself no longer works. It does work in Gutsy. The app just freezes after a few seconds of use and parts of the window forms go black or look strange. When running with mono --debug I get no messages. I tried taking different parts of my code apart and I found the issue seems to be caused by the use of system.threading. I ran a console app using threading but could not reproduce the error. Next I made a new very simple window forms app that uses threading. Got the error. I've attached the code for this program. To reproduce this error just compile and run that program on Hardy. Click the button1 to create new threads and windows. Try clicking on some parent windows, since it's on a different thread it should let you click on them. This is how it works in .NET and the previous mono that came with Gutsy. Now it just freezes. The bug doesn't happen every time but after playing with it for a minute or so I reproduced it every time.
I did manage to get this stack trace using a mono --debug. Oddly enough I only could get it one time and I tried about 20 times.