GUI Toolkits for external with own window

Hi,

Has anyone had success developing an external with its own window using a cross-platform (WinXP/MacOSX) GUI toolkit?

I've tried several toolkits including Juce, wxWidgets, FLTK, and FOX, but I couldn't get them to work on MacOSX. Some don't work properly when run in a separate thread (e.g. input from keyboard/mouse unavailable). Other's crash intermittently, I think because they use the same non-thread-safe drawing functions that MaxMSP uses. Since most toolkits use a never ending loop to poll/listen/dispatch, running these loops in a separate thread is necessary.

I know this is a shot in the dark, but if you've had success with a GUI toolkit, please let me know. I promise I won't badger you with questions :)

Thanks,

Davis

P.S. I've already considered spawning a separate process and using IPC, OSC, or TCP/IP to communicate with the external.