I've been using v4 for a while now and generally have been fairly happy with it. I ran into a problem however when using it in conjunction with a newer release of truecrypt that leads to a BSOD when mounting an encrypted volume. After a bit of googling I saw that the BSOD problem had been fixed in v5 so I decided to upgrade. Initially I just installed v5 over the top of v4, but I kept getting lockups on boot. After a bit more googling I found a thread that recommended that you do a fresh install as installing over the top of v4 can cause some problems. So, after I did a fresh install, no change, still getting random lock ups. Another thing I noticed around this time was that if I did successfully manage to get booted in, after a few hours my networking stack would crash. I'd lose all network connection (even though the network status always showed connected), and if I attempted to check the details about a particular interface the panel was always blank. Something was horribly horribly broken inside the Windows network stack. So, I did a bit more digging and found a thread saying that another known problem was installing NOD32 onto a different partition than the one Windows is installed on (which I was), so I removed v5 yet again, and reinstalled it on my C: drive. That eliminated the crash on boot, but my network stack still dies after a few hours. Another thing that may or may not be related is that I at the same time the network stack crashes I get 101 popups (and if I close them they immediately count right back up to 101 which seems like some sort of cap) saying "The user rules file contains invalid data.". I think this may be a red hearing though as I've never configured any user rules. Also at this point if I attempt to open nod32 the window comes up but is completely blank (well, the green icon in the top right shows up but doesn't do anything when clicked on, and there's a scroll window in the middle, but it contains nothing). It's like nod32 is deadlocking somewhere deep inside its guts. My personal guess is that v5 has some kind of either deadlock, or else maybe some sort of buffer overflow somewhere in it, maybe a dangling pointer in one of the data structures. It doesn't BSOD, and the process still seems to be running, although completely idle, and it's not consuming massive amounts of memory (so no space leak), it's just... dead. Unfortunately for the time being I've had to revert back to v4, and just disable nod32 anytime I need to use truecrypt (fortunately not my boot partition). I'd love to upgrade to v5 again, it seems like a lot of nice improvements have been made, but until the above issues are fixed it's completely unusable for me.