Same problem here
Using a LN40B640R3FXZC. This TV dates back to 2009 I believe.
The problem occured for the 1st time this morning. My HDMI2/DVI signal (PS3) showed on all other HDMI ports, which means that when I wanted to use my cable TV on HDMI1, it didn't work.
I tried all you said, and nothing changed.
We just moved in a new house last week (12/07/01), so I thought that might have been related to that, but it is true that for the past 5 days, we've had a computer plugged in. We did have a computer plugged in for some time before and it never happened.
We played both Wii and PS3 last night.
Will unplug and re-plug today.
Just trying to help to find the causes here.