I need some help with tension problems on my sewing machine.?

I have been sewing for over 50 years but just got a new computerized Brother machine. It has an embroidery attachment and I love it. Have already used that feature alot. But..when I try to do regular sewing the fabric puckers up. i have tried to reset the tension several different ways, removed and replaced the bobbin, changed needles etc. The stitches look ok from the top and the bottom, but everything puckers. Do I have to use different thread than what am used to? Just good old Coats and Clark.