Mary, I have had this problem several times on my PRISM (OS/2 WARP operating system, v2.2 beta software). I do not have an autocarb device, but if the run stops due to the system controller not responding, it usually happens overnight during an equilibrator run. I have found that if you cycle the system controller, this problem stops---albeit for ~3-4 months between incidents. I can only surmise that there is some sort of static electricity charge that sometimes builds up over time. To cycle the system: a)shut-down the computer completely b)turn off system controller (should be an on/off switch on back of controller) c) unplugg source mains to high voltage supply (you can also try unplugging computer as well...) d) Leave source mains uplugged for several minutes. e) Plug mains back in, turn system controller on f) Turn computer on, and reboot software. Good luck, GAIL *^*^*^*^*^*^*^*^*^*^*^*^*^*^*^*^*^*^*^*^*^*^*^*^*^*^*^*^*^*^*^ Gail F. Eaton Analytical & Nuclear Chemistry Division Lawrence Livermore National Laboratory P.O. Box 808, L-231 Livermore, CA 94550 Phone: 925-422-9546 Fax: 925-422-3160 e-mail: [log in to unmask] *^*^*^*^*^*^*^*^*^*^*^*^*^*^*^*^*^*^*^*^*^*^*^*^*^*^*^*^*^*^*^