Perhaps this was obvious to all but me, but I thought I would post it anyway.
I am sure all SharePointers out there have seen, and perhaps been plagued by the above error. Well, there is now hope.
Go to the web.config file for your particular SharePoint Web Application, and open it in your favorite editor. At the top, set (forgive the XPath) '/configuration/SharePoint/SafeMode/@CallStack' to "true". Then set '/configuration/system.web/customErrors/@mode' to "Off". Finally, set '/configuration/system.web/compilation/@debug' to "true". Suddenly, your "Unexpected Error" becomes a "traditional" ASP.NET error that you can actually debug. Now why did I think of this before??
Big kudos to Jimmie Thompson from Microsoft Consulting Services for pointing this out.