I've had my 2000 since November and I love it - and never had had a problem with it at all. I'm wondering if your timing is off a little bit? I'd get it serviced/cleaned and see if that helps.
I don't know why you'd be having such horrible problems...
Having said that.. I had MAJOR issues with my Tin Lizzie sit down machine... and after watching and using this bobbin tension technique, it fixed my tension issues completely...
http://www.youtube.com/watch?v=Q1mRhcquZTM
I check every single bobbin because each one winds slightly differently. I haven't had an issue since. I don't use my Juki for quilting often - just small stuff or when I need a walking foot...