Seems as some of the Slims have problems with the HDMI port.
On a side note, I ALMOST left my copy of GOW collection in the 250GB PS3 that I returned. Oops!!! =P
I've been having this problem on occasion also. At first I thought it was my tv because I bought it at the same time as my ps3 slim. But the problem didn't start happening until about a month later, what I would do is try to wiggle the hdmi cable around but nothing and the only thing that works when it happens now is if I turn off the tv and turn it back on it clears the problem.... don't know if its the tv or the hdmi cable or ps3.
Stay in you lazyboy and try the remote. Just change to a different input. ie change to a OTA TV signal, or Cable, something other than HDMI.........then switch input back.
This was a workaround I used when the PS3 failed the handshake making my screen all useless.
I had the same issue today, had to push the cable a bit down to set it right, else it wouldnt show on my tv!
sucks that the port is loose since I dont want to do it always as and when I remove it to connect something else to my tv.