yeahh, i did..
No...more than likely its a bad memory controller on the board. I work for Fairfax county government in the IT department and have seen many of these optiplex gx 240 and gx 280 have the same problem. We always call up dell and tell them its happening on another pc. Its a known problem with those models and the techs at dell will tell you that you need the motherboard replaced. (and its not so they can get more money bc we get it all for free since its under warranty) Ive had to call dell on ten separate cases for that problem in the last 5 months