help

[tummymunkey.livejournal.com]

sometimes my sewing machine will pull one STRAND of fibre in a fabric...i don't know how to explain it better. like, it puckers where the strand is pulled...and it will pull in a perpendicular direction to where i'm sewing....it did this on dress pants....

what's making it do that? i adjusted my tension all different ways. i dont' think it's the needle....

???

thanks