the error that i get when i up grade from 7.0.26 to .27 or .28 is
"
5/31/2012 5:36:32 PM | | App version needs OpenCL but GPU doesn't support it
5/31/2012 5:36:32 PM | Milkyway@Home | Application uses missing NVIDIA GPU "

but just one line up
"5/31/2012 5:38:09 PM | | NVIDIA GPU 0: GeForce GTX 560 Ti (driver version 301.32, CUDA version 4.20, compute capability 2.1, 1024MB, 912MB available, 1382 GFLOPS peak)"

i have uninstalled the nvidia driver, boinc (so far as deleting it fully out of the program data folder), and i have been going around with this for about 4 weeks,

the reason that i need to upgrade to .27 or higher is because of the high usage bug in .26. but when i am running .26 i get my OpenCL that works.
this is on a win 7 64 bit

You might try updating to the WHQL Nvidia driver version 301.42. When I updated BOINC to the beta 7.0.28 version to get rid of the high usage bug, I started seeing the new OpenCL entries in the messages log at BOINC startup.

5/22/2012 7:12:31 PM | | NVIDIA GPU 0: GeForce GTX 460 (driver version 301.42, CUDA version 4.20, compute capability 2.1, 1024MB, 916MB available, 988 GFLOPS peak)
5/22/2012 7:12:31 PM | | NVIDIA GPU 1: GeForce GTX 460 (driver version 301.42, CUDA version 4.20, compute capability 2.1, 1024MB, 888MB available, 1021 GFLOPS peak)
5/22/2012 7:12:31 PM | | OpenCL: NVIDIA GPU 0: GeForce GTX 460 (driver version 301.42, device version OpenCL 1.1 CUDA, 1024MB, 916MB available)
5/22/2012 7:12:31 PM | | OpenCL: NVIDIA GPU 1: GeForce GTX 460 (driver version 301.42, device version OpenCL 1.1 CUDA, 1024MB, 888MB available)
5/22/2012 7:12:31 PM | Milkyway@Home | Found app_info.xml; using anonymous platform

Cheers, Keith

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This might be applicable...

Release Notes for BOINC 7.0

See notes on installed as a service:
Known Issues on Windows
Protected Application Execution (Service) Installation, GPU detection and Windows XP