Posted in the hopes it can help Hylander or anyone else who may bump into this in the future.
I trolled Google for a few minutes tonight, and after checking my system determined that the hard drive where BF2 is installed had been thrown back into PIO mode--much, much slower than UDMA Mode 5, which is what it should be. I found a site that explained why it happened and had a VB script to fix it here. I tested the script, and it did reset my drive back to UDMA-5; hopefully I should be able to play at a reasonable clip tomorrow night. We'll see....