ie6 freezes after upgrade from 5.5 sp2

OS is Win NT 4.0 with SP6a. After upgrading, at the home page, no page appears, an hourglass appears and no menus can be accessed. When I go to the Internet Properties and attempt to access the Connection tab, I receive a Dr. Watson error in Explorer.exe. Once I remove 6, 5.5 works fine. When I further try to remove 5.5, the option to Restore to previous Windows Configuration is greyed out. If I’m successful in removing 5.5, I get an incomplete version of the previous install which I can tell because the ie shortcut on the desktop is disassociated. I’ve tried reinstalling SP 6a but the same problem persists. I’m stuck at that point. Any ideas?