Not sure if ill get any help with this but worth a punt 
I've got the above lens (Canon 28-135 mm IS USM) been working fine no problems at all, up untill now when focusing on something the lens constantly keeps trying to focus when looking at the ring on the outside of the lens which reads the f stops etc.. it seems that it keeps focusing then going into macro then focusing all the time any ideas whats going on please?
hope that makes sense :$
Cheers
Jon....

