So far the problem appears resolved since last Thursday. I worked with a second Dell representative who called back, remoted in, and worked several other fixes using the Dell Click 2 Fix tool. I don't have the full list of actions taken, but several drivers were removed, the latest reinstalled, and the BIOS was updated/reflashed. If the problem appears again, I'll post again, but it appears corrected.
I'm not sure exactly where the problem occurred. While this was happening, I had everything fully updated to begin with.
Anyway, thanks again to Dell support- they responded within 24 hours of my contacts and we were able to successfully resolve the problem. I bought my system through a retailer but it was still under warranty.