Sessions look good, occasionally I actually get the page back if it does not timeout first. The 500 error is the timeout. Do you see anything in the code that could possibly cause a problem?
Your friends over here at WebAssist! These Dreamweaver extensions will assist you in building unlimited, custom websites.
These out-of-the-box solutions provide you proven, tested applications that can be up and running now. Build a store, a gallery, or a web-based email solution.