That's what he already believes is the issue, but it was most likely the tv firmware update that did it. We're just trying to work out if he can fix it from the PS3 side as LG aren't helping him.
TV update is definitely a likely culprit, LG may have messed with the code, forgot PS3 still exists and did the drivers only for PS4 or something. Doesn't surprise me they won't help, big appliance makers are not fond of dealing with customers directly.
Pretty sure it's due to Sony's implementation of HDCP, as I used to get the same if I use a HDMI switcher or physically disconnect / reconnect /switch source with my living room Toshiba TV. Not that it helps you, but a firmware update for my TV has greatly helped (still occurs if I use the HDMI source switcher though).
Through my Yamaha RX-V565 it only occurs if I power on the PS3 whilst in pass through / stand-by to another HDMI source, power on the amp, switch to PS3 HDMI source -> no video signal.
HDCP can be a pain, get too many steps involved and it thinks you're trying to pirate the signal or copy content illegally and throws a fit.
Was cinavia removed/added with the new firmware?
Also was there a powercut or anything recently? (trying to determine if something could of reset the receiver settings)
Do you run your HDMI cable through the receiver and then to the TV for the PS3? If so try hooking up the PS3 directly to the TV and then changing inputs and you'll see if the handshake issue is between the PS3 and TV, or either the PS3/receiver or receiver/TV.
Personally i only ever connect HDMI directly, too scared to try anything else after bad experiences with an HDMI splitter/switch back in the days when TV's had just one HDMI in but alas we had a PC and a 360/PS3 etc. It would often do similar things: either take forever to find the signal/feed, or require a hard reset of the TV.