Well I'm not sure what's wrong w/your Kenmore, but that piece of lint had to go. It's compacted lint, if I don't clean my machine often enough, it can look like a bit of felt under the throat plate!
I wouldn't recommend you put in a dif. bobbin or bobbin case, that will likely make it worse. Also put the compressed air can away, use it on your computer keyboard, it's not good for sewing machines, even worse for sergers if you have one. This from a machine repairman I used to work with...

Have you removed the throat plate? There may be some lint under there too. It 'should' pop off carefully (ch. manual). Have you adjusted the tension screw on the bobbin case? My Bernina dealer told me yrs ago NOT to try to adjust the bobbin tension, he said it can be hard to get it back to the right tension, that it's a very fine adjustment. I've read some blogs where people do adjust it tho. Are there any burrs on the inside or outside of the bobbin case? An emery board may be used gently to remove a burr. But then later you'll need to figure out WHY there's a burr. Are you changing your needles frequently? They can get burrs & bend if you're rough on them, which can cause bobbin problems.

Anyway, I hope you took a break from wrestling w/your machine before you got frustrated and possibly made it worse. You know it's guaranteed to happen when you want to finish a project, almost never when you're just sewing for fun. When I sewed in a workroom we were told to walk away when we got frustrated, it really saves time in the end by not creating more problems.

Back to basics, did you refer to the machine manual? Google your machine model? Check youtube? There may be a common glitch in your model someone figured out. I'd reset the tension, length etc to normal settings, oil it & insert a new needle. Make sure you hear the click when you insert the bobbin, try hand walking the needle up & down a few times. You can hear/feel where it's catching as you walk it. ALWAYS turn the flywheel towards you, never away from you, the gears are only meant to move in one direction. Are your bobbins wound properly? Wind a new one, don't put 2 colors on one bobbin & don't race to wind it (wind slowly). Next make sure it's in the case in the right direction, some are inserted clockwise, some counterclockwise. Check the manual for that, it 'could' be as simple as that. Also double check you've threaded it properly.

Hope you get your Kenmore running again w/out having to take in for repair. Here's another link where most point to tension as the culprit.
http://ask.metafilter.com/17423/Sewingfilter-loops-on-bottom-of-fabric

Here is a link that might be useful: troubleshooting info