the plauge is back?
http://www.chiefdelphi.com/forums/showthread.php?t=30041&page=2&pp=15
I know you know it exits because you posted there. In general it’s better to continue an existing thread. 
Just an FYI.
But I hope you find a solution.
You know, with all the rough handling the RCX gets, the batteries tend to push back the terminals. I have had success using a small screwdriver and bending them out so they make better contact. Once that is done, it is important to reload the firmware.