Boggot --
I ended up opening a support case with MSFT and the tech was able to help me define the problem a bit better. His argument was that the client was still installing, and this specific error line in the log was meaningless. However, the client still wasn't really installing correctly or connecting to the MP until it received the client from GPO / Windows Update. Nothing *after* the client installation would complete, and we spent a few hours on the phone digging through logs and what not, to no avail. Having the problem a bit better defined really helped though, as this thread on technet (http://social.technet.microsoft.com/Forums/en-US/configmanagerosd/thread/d774aa93-ebf9-4693-9480-c02ce13d859f) began to make more sense to me. That evening, I kicked off a new Build & Capture sequence with the additional restart, as recommended by clab1979 in the technet thread. The next morning I deployed it and it worked fine. I've been doing some more work with this to be certain that the issue is resolved, and so far it looks good. I'll update the thread with further info once I'm more certain, but I feel pretty good about this fix.
*UPDATE*
Just putting this note here in case someone hits this thread while troubleshooting. The reboot during build & capture resolved everything. It appears the issue has to do with the SCCM client attempting to install again using the settings from the first installation (during build & capture) -- it was trying to install to the D:\ drive (the Windows drive letter during build & capture, but not during deployment). There are a bunch of things in logs about it not having space on the D:\ drive (which doesn't even exist at this point), and my thought is that it's pulling settings left over from build & capture. That reboot mentioned in the technet thread above solves it all.