There could be alot of things going on. One place to start is if it is a table within a table? If the image is in the outer table, try adding background="" to the inner table. Also, specifically insert a bgcolor="" into every table declaration.
I've found that background="null" for the inner table works pretty well in getting around this Netscape problem.
I would also mention one more challenge: lots of browsers don't do well with a JPG background images for a table or table cell. They tend to get the size of the image wrong -- like making it twice as big - a nasty surprise.
If you can convert the background image to a GIF, things may be smoother.