Ah, so maybe the problem lies not with the depth of the seal but with the inside diameter being 2mm to big .

It didn't look particualrly oversize when i slipped it on though... Can anyone confirm that that part number is for the MC21 gearbox - or are they all the same?

Thanks for the links, pbekkerh. I have up to date Java plug-ins. I think . i wonderuif my firwall is the prob? I'll try switching it off.

Thanks again for the info.

Wb