With ClamXAV when it scans most stuff on my Mac Book Pro there is no issue but if I try to use it to scan the 'users' folder it seems to cause OS X to crash. If this is something that should not be done then it's not in the users manual as far as I can see nor does it stop you automatically like it does when you try to scan the whole hard drive. With the crashes the first time it happened the screen went into a thin 'mist' of little colour blocks. The second time it just locked up. Both times I was re-charging the laptop at the time & the laptop was recovered by the use of the power button to shut down & then to re-start.