Check your bobbin and make sure you have it inserted properly. I do a lot of free motion quilting and lint in the feed dogs shouldn't cause it to skip stitches because the feed dogs are down.
What size needle are you using? When I am doing free motion I change to a larger needle because it has to go through three layers. Is your metal free motion foot attached correctly? I know this might sound crazy, but did you lower your foot...because the feed dogs are down, I've forgotten to lower my foot on occasion and then felt really silly.... LOL
Hope you find that tomorrow everything works fine.. :)