Possibly the .dll file that handles .obj export/import is corrupt. I don't think you have to a full uninstall/reinstall, but a straight reinstall right over what you have should fix it. Or an install to another directory like Jim suggested might be a good bet. If you do reinstall over your current install, just be sure to back up your runtime directory and any custom files you might have inside your Poser directory.

If none of that works, just make sure you save some of that coffee for the morning after you're done with the beers.