IMHO, it is time to go to the 'doctor'! When you do, take in both feet (1/4 and little foot), maybe the 'dr' can advise you if little foot is the problem.

I can't imagine it's the thread. I've been using the same large spool of aurifil for my last three projects (and this problem never presented itself). I've re-threaded the machine a dozen times. I just discovered the last needle or two I had put in were size 90/14 quilting needles, instead of size 75/11 (which I ALWAYS use for piecing). I just sewed a few test scraps and so far it's better, but I still see bobbin thread on top (not as severe) with the upper tension on the lowest setting.

I've also tried with my previous 1/4" foot, and it's better than with the little foot. But I LOVE the little foot. The visibility is so much better that my seams are more consistent. Maybe I should just bite the bullet and tighten the bobbin tension.

Don't be afraid to adjust your bobbin tension. Turn the screw a quarter turn, rethread, and see if that makes a difference. Turn it another quarter turn if you need to. And, as an earlier poster said, do the drop test on your bobbin. It should drop about 6 inches and then hang from the thread. If it goes to the floor, your bobbin tension is too loose.

I'll do the bobbin drop test tonight when I get home from work. Am I going to mess anything up by tightening it? What on earth could have made it loosen on its own?

Also, when I adjust the bobbin tension, should I do my test stitching with the upper tension set at 0? My machine's upper tension ranges from +3 (tightest) to -3 (loosest).

How about looking and feeling for a burr on the bobbin, foot, or needle.

I had a problem like this. I tried everything that was already suggested and then I turned the thread spool upsidedown and that fixed my problem. Hopefully it will be something simple. Its hell when you have to take the machine in for repair!

Please keep us posted. Tension is so "iffy".....but I recently learned that it is OK to adjust the bobbin tension; prior to this, I thought that was taboo. Good luck.

You don't mention what brand of machine you have, but I had a similar incident with my Janome 6600. I tried everything to no avail. I finally turned off the machine and walked away. After calming down and returning, I turned on the machine, rethreaded top thread and bobbin thread.....tada! ....everything was good again. It seems that the thread came out of the tension discs, somehow. By turning the machine off and then on again, it reset.

I had my Viking do this same thing yesterday and never did figure out what went wrong. I just kept rethreading and kept trying to quilt. It would do fine for awhile and then start messing up again. Today it went just fine. There is no bobbin adjustment on the Viking so I may end up taking it in to the "doctor".

I've had this problem crop up randomly too. Usually it's too full of a bobbin. I unload some and it seems happier. Also, try a different bobbin - if that doesn't fix it - try different bobbin thread. Of course, if it takes oil, take everything down and oil it up real well. I feel your pain though. The only time I can sound like a sailor is when my machine starts doing weird stuff - it makes me so furious. Of course, I'm really only furious that I can't figure it out. Oh - also try turning it off and back on too.