I got this problem too. I remember I was still able to play M and B with my antivirus and firewall ON and it is working perfectly fine. But then recently my antivirus always notifies me of "Win32.Virut.CF" I am receiving notification that it has been removed. I performed deep scan. Everytime I find some security risk I remove it. Since that "Win32.Virut.CF" notification pops up, I could never play M&B again. I was planning to buy it even though iit uns lil bit slow in my pc because it is really good. But jeez, I think its this Win32.Virut.CF that is causing the problem. Its the culprit! Its persistent too, my antivirus removes it every time but it keeps coming back its like a ball that keep bouncing in a wall. I gathered some info about this virut and it says that it affects .exe files. So i suspected that this was the culprit! Everytime I double-click the M&B.exe "Themida" message appears.
Update 1
I currently turned off my system restore and started a FULL SCALE INVASION! I mean, a full system scan. Virut might be hiding in the system restore thing. I'll get back for results. (I still have m&B installed in my pc)
UPdate2
STill on the scan, its still gonna take about 1-2 hours. What I noticed was, at first I performed full scan, nothing was detected and its clean. But when I turned off system restore and started full system scan, right now I got 3 fully resolved and 1 partially resolved Win32.Virut.Cf.s' If I get free of this virut and M&B starts to work fine then I am sur that this would be the culprit.
UPdate 3
Scan finished, I restart the pc after getting 23 security risk removed but still, M and B wont run.