Actually, it's difficult to advise anything here, so I'll just list the options:

• The issue can be related to ANTS Profiler. There are some evidences exposing this. We use dotTrace to profile DO4, and nothing like this happens with it.
• Also, the issue can be related to PostSharp. There are some evidences for this as well, but in case with PostSharp itself it's really pretty easy to get such error, if you write your own aspects, since you can do generally anything with MSIL code. On the other hand, it's suspicious that application crashes just under profiler - i.e. likely, this mean this is more related to profiler, rather than PostSharp (esp. taking into account that nothing similar happens with dotTrace).

I think the best option is to check your assemblies with PEVerify to find out the reason:

• If there is something wrong with IL, we can try to fix the issue or notify PostSharp team about this.
• Otherwise I'd suggest you to notify RedGate about the issue. If this won't help, I can only recommend you to try dotTrace :)

But IMO, the worst part here is that .NET error reporting in this case is absolutely bad. It writes nothing helping to find the reason in this case. We've been getting this error for few times while developing our Tuples framework - originally it was relying on IL Emit, so we've been getting such exception while debugging it. But currently Tuples are fully based on generics - we switched to this option mainly to make them serializable. So actually, this error is pretty normal, if you use IL Emit, and I'm absolutely sure people using this API simply hates it. I understand Microsoft considers buggy IL normally can't appear - well, actually it can, even if you use only public APIs. So IMO, they should make the error reporting more descriptive in this case.