When ie starts to play up it can be tricky to fix as it's integral to os. Try, reverting to previous version; repair; reinstalling os over itself. If none of these work try:
DOWNGRADING FROM IE 6 TO IE 5.5
If you try the described method and "Restore previous..." is diabled, find the file iemigrat.dll and rename it to iemigrat.old. Reinstall Windows over the current installation (you will lose no data), then install Internet Explorer 5.5 SP2. Visit Windows Update for the security patches.