Just Restore from a earlier date in time, If you don't have a saved "earlier point" then I would say you'd have to go in and find the program that is causing this problem...( check your recent downloads etc etc ) and start un-installing them one by one.
Once the problem stops you'll be able to find out what program was causing this.
And if you had to un-install something that you need while in the process of finding out which program it was just simply re-install it.
This would be the hard way of course ..but this is also "the end of the line" option of finding out what is causing your problem.
I hope this has helped