Have you tried changing the file extension for system restore to get it to run as certain types of viruses/malware can prevent .exe files from running.
A .com extension will run the same as a .exe and can fool them into allowing them to run.
Go to folder options in control panel and deselect hide extensions of known file types.
The restore program is found in c:\windows\system32\restore folder. select rstrui.exe, right click it and click rename. Rename it to rstrui.com and then double click on it to run system restore and restore your computer to an earlier time.
This will hopefully remove the virus/malware that is causing your problem.
If this works you will then need to turn system restore off and then on again to remove all the restore points so you can not do not accidently restore at a later date back to the same problem.