|So IE opens, you go to Tools > Manage Add-ons, then nothing happens (no Window arrives)?|
If this is your issue then I can only suggest IE Repair:
You don't say which IE version it is but most are covered in the above link.
Best to first try the MS Fix-it that appears on the above page (Add-ons are listed as one of the things it fixes).
IMPORTANT - Please come back and let us know the outcome.