Red Light On The Upper Right On The Back Of A Dell Poweredge 6650 Blinking-why?

The user guide is here: http://support.dell.com/support/edocs/systems/pe6650/en/ug/305utc11.htm#1058406

Dell status indicator lights are typically blue.  It will flash amber if the system has an error.  The various Dell servers I've worked on only have red indicator lights which are located INSIDE the server.  If this is what you are referring to then it's a motherboard status indicator and may be ignored unles you are fixing a problem.

The message you noted is listed in the user guide as "Multiple single-bit errors on a single memory module." which would seem to indicate you have a bad memory module.  Try running memtest86 from a floppy or CD to identify the bad stick of RAM.  Alternately you can remove sticks in pairs until you isolate the bad one.