I am experiencing occasional hung CUDA work units, just a few times a day on each CUDA capable machine. If I suspend the hung work unit until another CUDA work unit starts, then resume the hung work unit, it eventually restarts and completes normally. GPUGRID work units don't seem to hang up. I have 5 CUDA capable computers (Windows XP Service Pack 3) and I'm running SETI@ Home (CUDA 6.08 on BOINC 6.6.2) (also GPUGRID) on all 5, as well as World Community Grid, & Einstein@home. Below are the specs for my 5 CUDA capable computers:
#1 Intel Core 2CPU 2.40Ghz 1.98GB RAM GeForce 9400GT 512RAM Driver 6.14.11.812
#2 Intel 2 Quad 2.40GHz 1.98GB RAM GeForce 8400GS 512MB RAM Driver 6.14.11.812
#3 Intel 2 Quad 2.40GHz 1.98GB RAM GeForce 9600GT 512MB RAM Driver 6.14.11.812
#4 Intel 2 Quad 2.83GHz 1.98GB RAM GeForce 9600GT 512MB RAM Driver 6.14.11.812
#5 Intel 2 Quad 2.83GHz 3.25GB RAM GeForce 9600GT 512MB RAM Driver 6.14.11.812

I've also posted this message in Q & A, under CUDA

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Several people are having this problem. The way to get around most of the hangs is to run benchmarks on a regular basis...every hour or two seems to work. You can get instructions here:

http://setiathome.berkeley.edu/forum_thread.php?id=52078

Or more info here:

http://setiathome.berkeley.edu/forum_thread.php?id=51539

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You will be assimilated...bunghole!