What do you do when you have a page that consistently hangs in IIS? Typically, you start with standard troubleshooting techniques...what's changed since the last time it was working, are there parts of the page you can separate out to isolate the faulty code, etc.
If you've tried all this, and still haven't gotten anywhere, you might want to try the IIS Crash/Hang Agent and IIS Dump, which can help you gather information about what's going on when a crash or hang occurs. You can also use this information to help Microsoft support understand the problem, if you choose to open an incident with them.
There's also a webcast video available on IIS.net covering hangs in IIS, common reasons for them, and how to resolve them more quickly.