[mythtv] HELP: CentOS 6.3 install "MYTH_PROTO_VERSION was empty."

[Richard Shaw]

I "upgraded" my combined FE/BE from Fedora 14 to CentOS 6.3 today and
I'm running into the following issue:

2012-12-08 17:07:44.033219 C  Protocol version check failure.
			The response to MYTH_PROTO_VERSION was empty.
			This happens when the backend is too busy to respond,
			or has deadlocked due to bugs or hardware failure.

Also, mythweb gives me the "Can't connect to 192.168.0.4:6543..."
message even though the backend is running.

I've got 192.168.0.4 specified in both places in mythtv-setup (but
still have ::1 for the ipv6 which I'm not using).

I can't find ANY errors in the backend log. Everything seems fine.
SELinux is disabled and I've tried with the same result with iptables
stopped.

I even tried backing down to 0.25.2 with the same result...

Thanks,
Richard

Obligatory system info:
# mythbackend --version
Please attach all output as a file in bug reports.
MythTV Version : 0.26.0-3.el6 (v0.26.0-55-g09ac5b2)
MythTV Branch : fixes/0.26
Network Protocol : 75
Library API : 0.26.20120822-1
QT Version : 4.6.2
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