Many users have reported this problem here and on the official EQ forums, since the Omens of War patch. If you are using an NVIDIA card, multiboxing EverQuest will cause system crashes, regardless of other software running (WinEQ, EQWindows, EQPlayNice, etc). Although I will do what I can to help identify the problem, I unfortunately am not likely to be able to provide a fix since this is an issue in EverQuest. Please use the official EverQuest forums to report you are having this problem.
Here is one of several threads on the official forums about this issue
http://eqforums.station.sony.com/eq/boa ... e.id=68538
Here is a thread from users here that seem to have solved this problem
http://www.lavishsoft.com/forum/viewtopic.php?t=792