No promises at all but a system Reset cures many ills:
Hold down the on/off switch and the Home button simultaneously until you see the Apple logo. Ignore the "Slide to power off" text if it appears.
A Reset does NOT delete apps, photos, movies, music or any other data.
Also, you might wish to download the 4.2 User Guide. Pay special attention to page 170.
http://support.apple.com/manuals/#ipad