I took the plate off last night and cleaned it all out. I got a TON of fuzzies out of the bobbin casing! (It was pretty gross, considering I've only had the machine about a month and a half!)
I am using the same cotton material that I've been sewing on for days, and the same thread I've been using for weeks. Same thread in the top and bottom; I fill the bobbin from the top spool when it runs out. The bobbin is about 1/3 full, though it was about 3/4 full when it started acting up - it's wasted that much.
The feed dogs are up, I even moved them up and down several times while cleaning to make sure they aren't clogged with lint. The needle seems fine, but I'll change it anyway, just in case.
I guess I'll have to wait and see what it does tonight when I try again. Hopefully the Gremlins are done playing around and will let me finish my project!
Thanks for all your help and suggestions! I was beginning to think I was losing my mind! Glad to hear this is a 'normal' thing. (I think? LOL)