I'm blaming Angie for this!
Yesterday while routing, I think I thought I heard a clunk when the X Axis changed directions once in a while, but I wasn't sure, and the routed stuff coming off the machine looked great. Well, after I was done routing last night, with the steppers still powered up, I gave the gantry a couple nudges, and the far side had probably 1/8" of movement. I'll dig into it this morning, and hope it's just something loose, not something broken!
Wish me luck!