Instead of holding onto an acquire over the duration of an entire frame,
acquire, copy to a texture, and immediately release the lock.
(Note from Jim: When it comes to synchronization, the idea of acquiring
a lock, and then releasing all the way in the next frame just feels a
bit worrisome. Especially when it's a GPU object. But at this point, I'm
just making shots in the dark in an attempt to eliminate any possible
things that might even have a remote chance to trigger latent bugs in a
GPU driver or the kernel. You know, that whole system freeze thing. This
probably doesn't have anything to do with it, at this point I have
nothing but wild geese to chase. Whatever.)
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