Problem Solved

I'll post this in the hope that it will help someone else:

We have a laptop that worked fine with my login but when another user logged in (successfully) he could get to Outlook but not to any of the network server shares (he could also get to individual computer shared drives). I could ping, I could access the laptop drives from other computers, the this user could reach network shares when he was logged in on other computers. Depending on if I used Windows Explorer, Net View, Net Use, or looked in the Event Log, it would give errors such as:
access is denied
Windows cannot bind to ourdomain.com domain. (invalid credentials)
specified user does not exist
user name could not be found ourdomain.com is not accessible

I tried manually specifying network settings, removed and readded the computer from the domain, then I noticed that when I tried to go to our intranet page that requires you to login that it defaulted to the user's first initial and last name instead of just their first name which is what we use for usernames.

That got me suspecting that something was storing his credentials as flastname instead of as firstname. I finally discovered that there is a new "feature" in Windows XP that will store your username and password for you, and guess what username it was trying to use: flastname. Don't ask me how it got there.

Here is how to get rid of it:
Go to Control Panels, User Accounts tool, and on the Advanced tab, click Manage Passwords. From here you can either delete the domain for which it is storing the values or you can correct the username that it is using.

See Microsoft Knowledgebase Articles: Q281567 and Q281660