Have you tried resetting your cable/sat box to see if a reset does the trick? Often times, if you call the cable/sat service provider, they can install updates while you're on the phone to correct this issue.

If that still doesn't fix it, then I'd recommend having the unit serviced. You shouldn't have to remove HDMI inputs to get them to work after both units have been working previously.

The only other possibility would be to try a different HDMI cable. It's possible that the HDMI cable may have a syncing problem.

Keep me posted.