AMD cpu ; Windows 7 Pro 32-bit

I like to 'Lock this Computer' (Windows button + L) when away from it but noticed the GPU becomes unusable and no GPU projects do any work (see BOINC Log excerpts below).
Confirmed the same problem using 3 NVIDIA drive versions. 296.10, 295.73, 285.62.
This is not the screen sleeping problem. All Control Panel Options are set to
Never Turn Off Screen, Never Sleep, Never Hibernate...

Is anyone able to 'Lock this Computer' and keep the GPU projects working?

=========
VERSIONS :
NVIDIA GPU 0: GeForce GTX 550 Ti (driver version 296.10, CUDA version 4.20, compute capability 2.1 ...
NVIDIA GPU 0: GeForce GTX 550 Ti (driver version 295.73, CUDA version 4.20, compute capability 2.1 ...
NVIDIA GPU 0: GeForce GTX 550 Ti (driver version 285.62, CUDA version 4.10, compute capability 2.1 ...

[Logging on to user's account]

15:32:44 | GPUGRID | Restarting task I4R160-NATHAN_FAX4-21-100-RND3608_2 using acemdlong version 616 (cuda31) in slot 0
15:32:44 | Einstein@Home | Restarting task p2030.20110422.G41.44+00.29.C.b3s0g0.00000_640_1 using einsteinbinary_BRP4 version 122 (BRP4SSE) in slot 1
15:32:58 | Einstein@Home | Restarting task LATeah2379A_96.0_800_-1.1e-11_2 using hsgamma_FGRP1 version 23 in slot 2

[Now Lock this Computer and wait a few minutes.]

15:34:59 | | GPUs have become unusable; disabling tasks

[and, log back on to user's account.]
15:47:28 | | GPUs have become usable; enabling tasks
15:47:28 | GPUGRID | Restarting task I4R160-NATHAN_FAX4-21-100-RND3608_2 using acemdlong version 616 (cuda31) in slot 0

[further to message 112264]

I also have just tried this beta driver : 301.24

NVIDIA GPU 0: GeForce GTX 550 Ti (driver version 301.24, CUDA version 4.20, compute capability 2.1 ...

Does not seem to act differently. BUT ...

I observe NOW (and possibly the same with earlier drivers, but have not yet confirmed) that I can 'Lock this Computer' (Windows key + L) and, as long as 'Switch User' is not attempted by anyone, I can Log back on to my Windows User Account and the GPU HAS REMAINED active, and doing some work.

This might provide a clue that changing the screen's resolution DOES cause GPU to cease project work. When I try 'Switch User' my screen does change its resolution, and changing screen resolution while staying logged on to my user account also stops GPU work.

So, I conclude, I can CAN 'Lock this Computer' while I am away from it for extended periods, manually power off the screen, and as long as 'Switch User' is not attempted, the GPU will keep working on its tasks.

Does anyone other than me care? ... I didn't think so. But I am now.

[ yet another addition ]

I should mention that my monitor is connected to the motherboard's onboard VGA port and that the GPU does NOT have any monitor connected to it.

When I change screen resolutions it is happening with the onboard video and not the GPU.

I have an ATI GPU that's used for my primary monitor, and I use Winkey + L all the time without any negative effect. Have not tried switching users. Windows 7 Home Premium.

From my frustration running GPU WUs on Windows, I learned a few things anecdotally that are probably at play here.

Since Vista, only the owner of the desktop can use the GPU. Therefore, when the session is locked, the user doesn't own the desktop anymore, but another user's process using the system account that displays the login screen. Therefore, an user's GPU WUs cannot be run anymore because Windows is denying his processes access to the GPU.

Depending on whether one's computer is in a domain, when a session is locked, instead of the login screen, one gets the unlock screen, whose process still belongs to the session's user, when his GPU WUs can run normally.

In my case, I gave up running GPU WUs on my system at work. Not so much because of this issue, since the system belongs to the company's domain, therefore unaffected by it, but because I want BOINC to run as a service so as to guarantee that it runs after a reboot, since sometimes I'm not able to login immediately to start BOINC up when I login, as the reboot often happens overnight or when I'm out of town or in a vacation, as luck would have it.

HTH

Augustine provides a good summary of what happpens in my case too.
I am happy as long as I lock my Windows user account while I am away, and turn off the monitor. This is working well for me.

Thanks.