I'm running 3.4.2 just fine on Win7 Pro x64. Did you remember to load a gadget prior to hitting 'Play'? My game crashes otherwise.
7600 Ultimate 64b
Windows Sidebar with gadget on desktop
UAC: Off
All PlayOnline/Windower related executables and files are set to "Run as Admin" within properties.
All PlayOnline/Windower related executables and files are set to "Compatibility mode: Windows Vista SP2".
3.2.2 hook.dll
All plugins running just fine.
My only problem, and biggest hate for 3.41 on W7 with the 3.2.2 hook.dll is that it does NOT support controller recognition for independent windows when dual boxing. So if you try to tab with a controller, or try to control multiple windows with one character, 9/10 it won't work.
On the other hand, it works just fine with 3.4.