iMac Time Machine HDD and Internal HDD failed at same time
Viruses or malware do not (generally) cause hard drives to fail.
This was asked some time ago - so did you solve the problem in the end and if so, how?

For the record:
Save the Console log files if this happens again. Using these files it is possible to limit the source of the problem to software or hardware issues. It is rather unlikely that two disks fail simultaneously due to independant reasons. Are you working in a hot or humid environment? Do your devices have surge protectors between them and the power outlet?