|You did not give any details like what you were doing when it happened and what you have tried already.|
Try restarting your computer first (It will clear out memory errors and full memory problems)
Second, update antivirus/antimalware program and scan
Third, open task manager (control/alt/delete) and see if there is anything running that shouldn't be (including an invisble version of internet explorer "iexplore") <you could try this before restarting> Google anything your not sure of.
Fourth, post back results.