I get a crash with this message: Access violation at 0x7c91084b (tried to write to 0x00040FFC)

This is caused by a bug in the Windows operating system. The crash address might also be slightly different, for example, 0x7C9108B. In particular, dual core CPUs such as the Athlon 4400 X2 and Intel Duo chips provoke the problem. Microsoft's description of the problem can be found in their knowledge base article, but in our opinion, it's a much more serious bug than the article describes.

Quoting from the Microsoft web site:
"Without these updates, computers that are equipped with these power management-capable, mobile, dual-core processors may experience decreased performance or unexpected behavior"

They say the solution is to download a hot fix, but at the moment (April 2006) Microsoft don't make it available for download. You need to E-mail or phone them first, which is far from helpful. Further discussion and references to alternative download links can be found in our forums.

Since PerformanceTest release v6 (build: 1012), we have worked around the problem and a host fix from Microsoft should no longer be required.