Nacra -
thanks for the ideas. I've already done everything you suggested except changing the bobbin; will have to try that.
based on the fact that the problem cropped up suddenly, I suspect the machine, which is 20+ years old and never serviced, could have "slipped a gear", or the layers of material caused a problem.
I'll try changing the bobbin and see what happens.
thanks to all for the help.
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