Chances are your profile data is still there. Go to your Netscape install directory and then go to /users (not in /communicator). See if your profile data is still there. There will be files for each profile you have.
If it is still there, you have two options:
1) Copy your /users directory to a safe place for now, uninstall Communicator, and then reinstall it. See if it now works.
2) This sounds like a good chance for you to upgrade to something else like Mozilla or Netscape. To the best of my knowledge, both of them will import profile data from Communicator in versions 4.5+.
If your profile data isn't there, sorry to say your data is probably lost.
UserAgent: Mozilla/5.0 (Windows; U; Windows NT 5.1; en-US; rv:1.4) Gecko/20030624 Netscape/7.1 (ax) Mnenhy/0.6.0.104