Maybe try running the system file checker: From an administrative command prompt type: "sfc /scannow" without the quotes (note there is a space between sfc and /scannow) and let that process complete which takes a few minutes. When it's done it will tell you if it found and repaired any corrupt system files.
Another thing you could try would be to create a new user account and from within the new account, copy over your entire old account (all the folders below your user name) to the new account. Of course, that might just result in importing your current issue to the new account, but you never know. If it doesn't work, you can just delete the new account. If it does result in a fix, then once you are sure all your data etc is in the new account, you could delete the account with the problems.
Finally, you could try doing a repair install of Win 7. This leaves your programs, settings and data intact. But if the problem is being caused by one of your applications, then none of these suggestions are likely to resolve the issue. You would need to start troubleshooting to determine which application or
driver might be causing the trouble.
If when creating a new user account, the new account really functions normally, I suppose another approach would be to create a new account and start installing your apps one by one and copying over your data and just setting everything up again. If problems start suddenly again after installing something, then that last installation is probably the culprit.