ANOTHER UPDATE
Okay, I discovered that there is
some
truth in this. Although misleading in forecasts of doom, there is a time activated virus with the potential to damage files on your PC. It's considered low risk, read info at the following if you want technical info:
http://vil.nai.com/vil/content/v_138027.htm
http://www.symantec.com/avcenter/venc/data/w32.blackmal.e@mm.html
Summary in basic terms for those who want to panic
If you don't have UP-TO-DATE antivirus installed, AND have ever opened a specific dubious email attachment, then on the 3rd of every month certain files on your computer may be at risk. Basically if you are at the bottom of the food chain, unlucky.
Additional for normal people
Just another virus folks, like the many others discovered each week. If you have AV make sure it's up to date, and don't open suspicious emails. Sorry for wasting your time.