Sigma 75-200mm F3.8 auto focus

Just picked one up, not had chance to test it to much but I have noticed its back focusing a lot in live view but is fine through the view finder. Was just wondering if anyone else had one and if this is this a common problem or just my copy of the lens? Thanks in advance.

I just picked one up this morning too at a boot sale... so snap (nearly!)
Looks to be a pretty sharp lens, better than I expected. I don't normally try and focus with liveview but tried to see if I could so as to see if I could answer your question. However I find that I cannot hold the camera steady in liveview mode - just how do you hold and aim a long telephoto lens using liveview, in this case set to 200mm (300mm equiv) and take a photo? I know I could have set it up on tripod but got perfectly good results using it normally. The liveview shot I took wasn't even what I aimed at and had dreadful camera shake!

A little later....
Now tried again with a tripod. I couldn't detect any off focussing issues with liveview.

John