I encountered wacky runtime errors on a particular .aspx today with
assembly DEIWSLA.DLL or one of its dependencies not available
Each time I reloaded the page another dll dependency with another name like SI-SST-A.DLL or JIQREAH.DLL was not available.
Though I may have complained early on about some of the W2K3 default settings for the web developer to get up and running, it doesn't take long to get into “W2K3 security mode” and like Greg Reinacker said to think of the W2K3 doors and windows being closed compared to being open in W2K.
The runtime provided the path of the dlls: c:\windows\temp. (sidebar: man, I think .net runtime errors are great!) Checking the permissions on c:\windows\temp, server\users had no permissions and domain\everyone certainly had no permissions. I gave the account servicing the site's web application pool, and everyone was happy. Especially me.