300mm F4 IS, IS system gone beserk!

Don't know if anyone has had this problem before but my 300F4 IS has developed "Saint Vitus" dance in the IS system.

The motor seems to have dropped its bundle and the image (with IS on or off and in manual focus) constantly jumps and an awful noise comes from the middle of the lens.

I am wandering whether I can have the IS disabled and revert to a non IS lens (I never use the IS anyway)

Any ideas welcome.

Chris

I've read posts about IS unit failures, however I didn't think it would effect the lens when IS was turned off. Either way I think you'll need a trip to canon service - might as well get the IS working even though you don't use it...