[mythtv-users] Broken 9.10 mythbuntu - questions

[Jonno]

I need some advice. I had been running Mythbuntu 9.04 successfully for
the past 7 months or so but since I upgraded to 9.10 I can't watch
recordings or LiveTV for more than about 30 mins without a frame
buffering issue causing a failure.

If anyone can supply answers to the following questions then I hope it
will help me either debug the problem or find a solution.

1. How can I check if there is a problem with the tuner card (pchdtv
5500)? I seem to get decent signal strength. Is there a utility I can
use to test it? All my signals are ATSC OTA so are raw mpeg2 I think.
I don't do any transcoding.

2. How can I test if there is a problem with my HDD. I have my
recordings directory mounted on a 1TB SATA drive which is plugged in
to the m/b SATA port but housed in an external eSATA enclosure with
it's own power supply. It is xfs formatted and mounted with
allocsize=512m. I've run hdparm a couple of times and get something
like:
 Timing buffer-cache reads:  1000 MB/sec
 Timing buffered disk reads:  100 MB/sec
The drive does seem to be increasing in fragmentation quite quickly.

3. My backend log contains a lot of this when recording:
2009-11-23 06:59:00.711 [mpeg2video @ 0x7f0cbd3c7820]ac-tex damaged at 50 0
2009-11-23 06:59:00.712 [mpeg2video @ 0x7f0cbd3c7820]00 motion_type at 26 3
and my frontend log contains the same messages plus a lot of this when playing:
2009-11-22 21:55:10.796 [mpeg2video @ 0x7f35b0d89820]Warning MVs not available
2009-11-22 21:55:13.384 [ac3 @ 0x7f35b0d89820]frame CRC mismatch
2009-11-22 21:55:13.415 [ac3 @ 0x7f35b0d89820]incomplete frame
2009-11-22 21:55:13.416 [ac3 @ 0x7f35b0d89820]invalid frame size
I've no idea what this might refer to. Since I'm recording straight
from OTA signals I didn't think this would be very taxing on my system
which is:
Asus P1-AH2 Barebones System with on-board Nvidia 6150
AMD Athlon x2 2.3GHz
2GB DDR2 SDRAM 800
320GB Internal IDE mythtv boot drive
1TB SATA drive for recordings

4. If I can't figure out what the problem(s) is(are), what are my
options as far as upgrading mythtv? I've never built something from
source so:
a) is there a repository I can add for updated mythtv (0.22-fixes?)
rather than the static Mythbuntu one? This would be the easiest option
for me but I don't know if it exists.
b) what would I need to do to go back to 9.04? Will I have all kinds
of nightmares with databases?
b) if I have to build code where do I need to go to start learning how
to do that? I've done some googling about svn but I can't find much to
explain this stuff to a non-programmer.

Thanks in advance for any help or suggestions.

Jonno.