you can ctl-alt-del to get out of it. I use the windows key to bring up the START menu - it gets minimized then. Doesn't seem to cause any problems. the only odd thing it does for me is it will "crash FROM desktop", like sometimes it will just un-minimized itself - this only happens if I have closed other programs, have NWN minimized, and am at the desktop. Watch out for that one if you're at work
all in all NWN seems to play reasonably nice, most games have their little quirks in minimizing in my experience.