Have you actually checked your file permissions on your Windows font cache and the Adobe folders? Checked security tools and otehr utilities that may interfere? You can reinstall all day, but if you don't fix the actual cause of the problem you only waste your time.
Welcome to the Forums. As Mylenium has already mentioned that the issue could be with the permissions, you may try to run the program as an administrator and check if it opens up.
You may also want to look at any recently-added fonts. Remove the new ones and see how AE behaves.
After you take care of any permissions issues, of course.
Thanks everyone for your help - as Anand said the run as administrator seemed to fix the problem!