Hello Gill,
First of all try and slacken of the presser foot by the dial on top,
failing thet you may need to raise the presser bar a fraction, if the presser bar was loose top begin with slacken off the pressure completely put the presser foot up with the lever then then slacken off the screw on the bar and adjust the presser bar.
drivewithken@blueyonder.co.uk, April 2008