Currently Being ModeratedJan 13, 2013 9:21 AM (in response to Katmandu123)
No viruses are out there for OS X however there can be other types of malware. The best method of keeping yoru system free and clear is keeping it up-to-date by running Software Update and installing the recommended updates. Also NEVER every download software from a site you don't trust 100%, if a site "tells" you you must download something then navigate away from that site.
You said your system isn't networked, please clarify. I'm assuming you are using it to access the Internet, if so then it's on the biggest network there is the WWW. Your screen issues could be cause be the need to do some basic resets such as iMac SMC and PRAM reset and restarting in Safe Mode which will clear some caches.
Currently Being ModeratedJan 13, 2013 9:22 AM (in response to Katmandu123)
It's almost certainly not a virus. Sounds hardware related, maybe the grahics card is going south. Run the Hardware Test in extended. Not a great diagnostic, so coming up negative won't be all that meaningul, but a positive can be trusted.
Currently Being ModeratedJan 13, 2013 9:23 AM (in response to Katmandu123)
What year was your Mac made?
In any event it is failing in someway. None of that stuff happens to a good working system. Virus? I doubt it. Attack from outside? You say it isn't networked so how could someone get to from over the internet.
Currently Being ModeratedJan 13, 2013 2:16 PM (in response to rkaufmann87)
I'm up-to-date on all updates, etc. You're right, of course, about the web being the world's largest network. I meant to say that it's a home computer not tapped into any LAN.
Currently Being ModeratedJan 13, 2013 2:17 PM (in response to WZZZ)
Ran the test before I put the question on the board. I also had the machine stress-tested at an Apple store. I'm beginning to think gnomes are involved.