Are you posting on the affected machine - but you do need to give more info as Shane has asked.
Infections can cause this problem and running a scan with an effective anti malware scanner would be best before attempting any remedial action.
Had you downloaded anything prior to this error message ?
If it is due to an infection, your restore points have probably been knocked out but if you can boot up into Safe Mode with Networking and have an Internet connection, download/run a scan with ESET Free Online Scanner
http://www.eset.com/us/online-scanner/Click on Advanced and check all of the boxes except the proxy one then disable your AV program immediately before hitting the Scan button.
This scan will take some time depending upon how much you have installed.
If you don't have Internet connectivity and an anti malware scanner installed then boot up into Safe Mode - go Start - type mrt.exe - press enter and select the Full scan and let us know if anything has been found.