When used in conjunction with the VisualStudio 2008 debugger, cfix may hang indefinitely as soon as an assertion fails. The reason for this behavior is a Symbol Server-caused deadlock between the debugger and cfix. I am going to discuss the details of this deadlock in a separate post.
Until a new version of cfix is available, you can work around this problem as follows: Go to the cfix installation directory and rename or delete symsrv.dll. This will stop cfix from contacting the symbol server. While cfix now will not be able to capture proper stack traces any more, this will prevent the mentioned deadlock situation to arise.
The problem only applies to cfix 1.1 and VS 2008. The problem does not occur when debugging with VS 2003, VS 2005, or cdb/ntsd/WinDBG.