Try going back to an earlier restore point first. If you've never done this, Go to Start / All Programs / Accessories / System Tools / System Restore
check the box to Restore my computer to an earlier time and click on Next. You'll see a calendar with highlighted dates. Choose one of the dates just preceeding these problems and allow your system to return to that date. See if the problem goes away.
For Vista: http://www.bleepingcomputer.com/tutorials/...43.html#restore
If the problem does not go away, go through the same instructions to reach System Restore and select the option to reverse the change.