There seems to be some wierdness in the environment of the worker process application -- aspnet_wp.exe's path includes a question-mark. .NET's System.IO.File namespace seems incapable of resolving this path, which seems to me a bug in the framework. See here
for more information.
Perhaps creating an application config file for Memory Tracker forcing the supportedRuntime to .NET 2.0 will make this work. I'm not in a position to try it right now, but I'll see if I can look into it later.