If you are running MOSS on Windows 2008 you can get an error whenever any file over 28MB is uploaded. This happens regardless of what the max upload size is set to for the web application and the usual error is a 404 File Not Found, somewhat confusing really!
When you make a change to the web app settings from Central Admin they do not get transfered to the web.config. So you must manully update the web.config for all web apps and all Web Front End servers needing this change.
You need to add add the following settings under the
section of the Web.config file found in
Inetpub\wwwroot\wss\VirtualDirectories\VirtualDirectoryFolder:
This solved the issue for me.