Problem: Updated my server 2003 and upon reboot I got the following error: The ordinal 421 could not be located in the dynamic link library urlmon.dll. The server would boot up but most functionality was lost from accessing the internet to checking log files. Tried a couple of things including replacing the urlmon.dll file within safe mode (the version of urlmon.dll that was on the server was an older version than it should have been). Still no luck.
Solution: Realized that the problem had to do with IE8. It turns out that IE8 did not install correctly and therefore created all of the problems. Went into “add remove programs” and uninstalled IE8 and rebooted. The error went away and functionality was restored.