Hmmmm, that is a strange one. The Chooser window cannot be resized.
Try this:
Go into the system folder>preferences folder & trash the following preferences:
finder
Apple Menu Options Prefs
Rebuild your desktop. Use
Techtool Lite or
Trash*Desktop (TD may delete Finder comments )to rebuild your desktop w/extensions off. Does a better job than manually & you avoid all the finger gymnatics. You just have to hold down the
shift key to shut off extensions.
Restart to turn the extensions back on again & empty the trash.
If you want to rebuild manually, see KB article
http://docs.info.apple.com/article.html?artnum=10182 Rebuilding Desktop File and Icon Recovery.
You may need to go back into the Control Panel>Apple Menu Options & reset any settings that you may have had.
Good luck