It’s one of those bugs… If you’ve tried profiling Silverlight lately and you’ve run into a consistent crash in Silverlight which brings down the browser, but only on specific projects then this bug is for you.
Basically, profiling any Silverlight app (plugin or OOB) that takes advantage of Shaders will cause Silverlight (and its container) to crash. The only current workaround is to remove the shaders before profiling (possibly with an #ifdef if you are so inclined). This is slated to be fixed in an upcoming version of SL 4 (though no release dates yet).
Note: people often get scared of crashes since they can indicate a security bug – but this is not a security issue (the profiler puts us into a bad state, causing the crash).