Thanks all!
Had already checked lint but it collects so fast sometimes and don't always get it all apparently either. Had almost new needle but will check that as well.

I would change needle and re thread machine and check bobbin

When I'm making bags and its real thick I also adjust stitch length.

When I had a Singer Athena 2000 it did this if I used a needle other than a Singer. Seems that the Singer needles were longer than most others and my machine needed the extra length.

I recently had this problem, and changed the size of needle (went from 90/14 to 80/12) and the seems to have solved the problem.

Another thing that has come up recently is that Organ needles are just slightly shorter than Schmetz. Organs work better on Janomes. So, the brand of needle and brand of sewing machine can come into play as well.

How long has it been since you had your machine service? My Janome 6600 had started doing this and after I had it cleaned and tuned up it had stopped and sewed like new again.

Rethread, checking for knots in the thread, new needle, drop of oil, clean out bobbin case, and try again. Usually one or more of these things will solve your problem.

Well I cleaned out the bobbin area again, took the needle out (may have been not in exactly right) and put back in, rethreaded top and bottom, and all seems to be working fine again.
So problem solved!!!
Thank you all.

The few times that this has happened to me it was the needle. I forget to change it out as often as I should, with the exception of changing from a piecing needle to a quilting needle. Hope this works for you, funny how particular our sewing machines can be at times and it can drive us totally goofy trying to figure out what the problem is.

And cleaned the lint from the bobbin area.