There's definitely a problem with the new version. I just bought Avast Internet Security 5.0 a couple days ago (version 5.0.462). As soon as the download was completed, my laptop (Dell Inspiron 1501 running Windows XP) locked up. I could move the pointer with the mouse, but that's it - I couldn't select anything with it, Cntrl-Alt-Delete to get to the task manager didn't work, nothing. The only thing I could do was power it down. It turns out, whenever I power up the laptop with my wireless router turned on (it connects to the internet automatically if it senses my network), the thing locks up solid. If I power up without connecting to the internet, everything is OK. So I disabled the firewall, and then I turn on the router, connect, and everything works OK. Oddly enough, I just re-enabled the Windows firewall (had been running with it off before because I had other firewalls) then, just for kicks, turned the Avast firewall back on. For the first time since I installed it, everything seems to be OK. CPU usage is nothing, memory usage is 6080K. We'll see if that keeps up. I'm extremely disappointed with the new Avast version.