Yeah, checking your port options should have been done for sure. I'm in about the same situation as you as far as inputs but my TV has everything that I need and more.
That whole thing about the TV auto-switching the input is rather annoying. Mine does it when I power on my DVD player. I find it rather annoying, especially when sometimes I just power it on to take a DVD out. Who thought that was a good idea??
OH, and I'll say again that my Vizio doesn't seem to have the slowness issue noted by you and Jake.