Hello Iris,
Welcome back to machine knitting.
If you remove the plastic cover at the back of the machine, you will see the punchcard mechanism. The timing belt passes round a drum which is connected to this with a series of cogs. Check that everything here is free from fibres and old oil and apply new oil to the moving parts. By running the carriage to and fro while set for patterning you will be able to see which bits move. If you continue to move the carriage you should be able to free up the mechanism. Once it seems to be moving freely, try it with a punchcard. Hopefully it will now select the needles properly. However if it is still very stiff and not working properly it would suggest that the plates inside the machine have stuck together and your machine will need a service.
I do hope you manage to get it working properly,
Regards,
Sue, January 2011