Is there anything else odd about that user account? Anything it can't do that the other account can?
It's possible that user profile is corrupt. The good news is it's a fairly easy simple thing to correct.
From Microsoft article 555473
To create a new user account:
Go to Control Panel.
Click User Accounts tool.
Select the Create A New Account link.
Give the account a name and click Next. NOTE: Ensure that the account type is Computer Administrator (You can see the option button displayed in the process.)
Click Create Account button.
Logoff from the current account, and login with the new account. This will create a user profile for the new account. When the user profile creation procedure is complete log Off from the account without doing any other modifications.
If that fixed the web access issue, then follow the instructions in the article to copy the profile settings from your old account to the new one.
Please post the results, good or bad.