I feel a clean boot can the issue. This seems to be like a third party application that is interfering with the normal performance of the computer.
To perform a clean boot on a computer that is running Windows 7, follow these steps.
1. Click Start, type msconfig in the Start Search box, and then press ENTER.
If you are prompted for an administrator password or for a confirmation, type the password, or click Continue.
2. On the General tab, click Selective Startup.
3. Under Selective Startup, click to clear the Load Startup Items check box.
4. Click the Services tab, click to select the Hide All Microsoft Services check box, and then click Disable All.
5. Click OK.
6. When you are prompted, click Restart.
7. After the computer starts, check whether the problem is resolved.
If your issue is resolved, follow the How to Determine What is Causing the Problem section in the KB article to narrow down the exact source.http://support.microsoft.com/kb/929135
Also, see the section on how return your computer to a Normal startup mode