I'm the maintainer of the Cloo project (http://sourceforge.net/projects/cloo/). After upgrading my ATI Stream installation to v2.2 (from v2.01), two things stopped working:
a) clBuildProgram() if a notify function is given (works with null) and
b) clEnqueueNDRangeKernel() if an event list is specified (also works with null).
It might be a bug on my side although I can jump back and forward between the two versions of Stream and reproduce the issues only on one of them.
I should point out that the project is a .NET wrapper, which may or may not be important. Perhaps you've changed something in your callback mechanisms? Because clSetEventCallback fails too (AccessViolationException). However, I'm not 100% that's Stream's fault, so let's focus on a) and b) for now.
I'm conducting the tests on an Intel CPU (SSE3 capable). Catalyst not present.
I could post some code if it helps you. It's not C/C++ though (surprisingly).