DIYbanter - Channel 3 fizzed out

Hello, I am not by any stretch of the imagination an electronics whiz or
enthusiast for that matter, but I am looking for a bit of information and
maybe some advice.
I have an old 'Panasonic - The one up' 68cm stereo TV set, about 10 years
old. It's done me pretty good over the years, not a problem. But, just
lately, Channel 2 started to suddenly fizz out - meaning the picture
disappears into grey fuzzies then turns blue, and the sound goes as well.
Sometimes it returns to normal within seconds, other times I have to power
it down and after 10 minutes or so, I switch the set back on and , presto,
there it is again.
Now channel 3 has fizzed out completely. I used to have my optus cable tv
stb
tuned in to this channel.
I have tried manually tuning both channel 2 and 3 over and over and I seem
to have success with channel 2 but channel 3 remains impossible to find.
The optus stb is also tuned into channel 1 on the VCR. It works fine through
that by viewing it on AV3. (I want to have the option of watching the optus
TV without the VCR switched on so please, don't suggest I just run it this
way.)
I have a second TV set on the same Aerial cable and there's nothing wrong
with channel two on that set when it plays up.
I don't have any trouble with any of the other free-to-air channels fizzing
out like this. Only channel 2 and 3.
I have rung OptusTV Service and Faults and described the problem to them.
They tell me I might have a problem with my TV set. I have checked all the
cables and connections...no obvious problems.
Whats going on? If there is a problem with the TV set, can it be fixed? and
is it likely to be expensive?
I realize it's difficult to diagnose the problem from what little info I
have given, but has anyone got an idea of what could be wrong with my TV
set? (in laymens terms if you can...hehe).
Any help/advice will be greatly appreciated.
Trev.