i have red quite a few reviews saying after 20 hours of play there is a bug that not only stops you from saving the game but totally wipes your hard drive saves of every game on it as anybody else had this problem and is there a patch to fix it.

Never heard of this bug. Only problems I have had are two freezes in 50 hours of play and a number of enemies stuck in the terrain. Other people hae reported other, more serious problems, but I haven't heard of anything like you mention.