Tamron 18-270 is stuck!

I have the Tamron lens mounted on Nikon D40.  I was taking pics today and seemingly out of nowhere, the lens stopped extending past 32mm.  It feels like it's stuck on something so I don't want to force it.  However, when I remove the lens from the camera, it seems to be fine.  Any ideas for fixing this at home or do I have to send it out for service?

Thanks,

Nicole