Dear all, I have a Sigma 18-250mm OS HSM lens that I've had for nearly a year now and love it to bits. It hasn't been bashed about and I'd like to think I generally take good care of it. However, since about January/February, I've noticed that occasionally I get an error when using it on my Rebel T1i (500D). I noticed it first when trying a bit of soft zoom-burst photography on a tripod (nothing harsh, very gradual) where I'd get an error message, something to do with the connection between the lens and the camera coming loose? I remove the lens and re-attach, and then it's OK again until the next time the error occurs. The lens was also tried on a friend's 400D taking regular static photos and it also gave periodic errors which required turning the camera off and on. Has anyone had this or a similar problem before and knows what's wrong with the lens? Visual inspection does not suggest any bad contacts or loose mechanical parts. Cheers!