I have a user here who had unexplained system lockups while browsing. It was occurring on Firefox 2, and continued after updating to 3, on XP Pro. There was little of use in the system logs to troubleshoot. However it was narrowed down to at least one reproducible scenario. Point Firefox at http://my.att.net/ and click the email button. There are ads which load on the left and on the right. Hit refresh one or several times and some set of ads or server redirects on the backend causes grief for Eset Nod32 v3 business edition. He had total system lockups with Nod32 6.21 and 6.50. Disabling real-time protection resolved the lockups. I today updated him to 6.69 (uninstalling 6.50, deleting the program folder and the registry entries, resetting TCP/IP stack and rebooting as per http://support.microsoft.com/kb/299357, then installing 6.69) and while it no longer locks up the system, it instead pops up a notification that ESET service has crashed and offers to send a report to microsoft. The service obviously restarts right away because I've confirmed that protection continues via EICAR download attempts. Thoughts, suggestions?