A client's computer's Firefox window is all black, nothing visible through it. He says it happened after he said okay to an update. I tried downloading new version of Firefox, didn't resolve. I tried uninstalling Firefox , downloading and re-installing. Didn't fix it. I tried system restore three times, different restore points. These didn't work ("system could not be restored").
As this computer is protected by ESET NOD32 which is up-to-date with no problems found, my gut tells me it is not malware. Though tomorrow I'll throw everything at it to see if there's some nasty thing hidden in there, it doesn't feel like a virus.
Any suggestions? Thank you.