My first thought
My first thought would be that the cable is bad. At least that's the fast and cheap option to test. What you describe sounds like the HDCP handshake isn't working, so you're getting a lower resolution as a default.
If the cable doesn't fix it, then odds are while unplugging the cable you damaged the port. Hopefully it was on the PS3 end, because that would probably be a lot cheaper to fix/replace than the TV.
Also, I would recommend checking out monoprice.com for the cable as opposed to paying the extortionist rates big box retailers sell cables for.