Royce,
What exact point are you referring to when you say user credentials? In the place where you enter a user? Or at the login screen.
A quick Google search on that error message, consistently says it is a VB error having something to do with the XML file in SQL. I believe AC is written in VB.
Depending on where you are when it crashes, you could look at or replace your .xml file. Also, given the VB possibility, maybe you should uninstall everything, and redownload the 4.072 and 4.073 and reinstall. If 73 doesn't work, go back to 72.
Let me know how it turns out.
