Unable to access OWA

Running a windows XP PC, can access every other site including other OWA pages (from ex5.5 and ex2k servers), but not the one the user wants. Not even able to load logon screen. Was working before and other PCs with same setup still work.

Have tried different WinXP logon, different proxy, LAN & DUN connections, PC domain membership, call by IP, flushdns, emptied cache, cleared objects (and plugins) and deleted all files in the temp folder for good measure.
Nothing has worked.

Any other suggestions? (besides formatting the hard drive)