91 300SL won't stay running

I had a problem similar to Colleen’s (and when I get the name of the part that was replaced I’ll post it, it was about $700 plus labor). But I digress - my car is still at the garage, it was already to come home, and they let the battery die. Then after jumping it or charging it, they can’t get the car to run for more than 15 minutes. I have posted on Mercedes Forums and someone thought they blew the EZL computer thing-a-majig. The mechanic swears he will figure out what happened even if they have to call the dealer. Lucky this is just my mid-life crisis mistress (faithful car at home), and as with many sexy, beautiful things, expensive to maintain! If anyone has any idea what the mechanics might have done, that would be great. It ran pretty good except for being sluggish off the line, which is why I brought it in.