Afraid not, I forget where I heard it. I ran a Google search just now, though, and found a few pages such as http://forum.bitdefender.com/index.php?showtopic=15070 which suggest Cygwin is innocent of such behavior and what's really going on is Cygwin needs a fixed DLL address (only for programs linked against it) and this is not compatible with some of the more intrusive antivirus programs that do inject a DLL into every process.