For the other Sue...

It sounds like your machine's timing is off - I had that problem with one of my antique Singers, it didn't matter what I did, it broke thread or knotted severely.

Not willing to throw my 1924 model 66 in the trash, or send it to Goodwill where I rescued it from, I looked around until I found a shop that would work on it. it turns out... one of the lower arms bearings were loose, which made the bobbin case run just slightly out of time.

Now, your babylock (I hope!!!) isn't as abused or old as this machine, but if you can't get the tension to tense right (after following the instructions on this page) it might be worth spending a few $$$ to have someone go thru it, and make sure it's timed right.

If you're lucky, you'll find a repair guy who will let you watch what he does. Not likely your machine breaks again, but if it does, yo'll know what he did to fix it. IF you're handy with tools (and can find the repair book for the machine) you'll remember what he did, and better, keep your machine running like the techs!!! ;)