My MythTV setup had been stuttering at very irregular intervals. It was very strange. I would watch a recorded show and at any time the screen would freeze and the debugging output would fall into a "prebuffering pause" loop and then after a few seconds fall back to mythfrontend. Just on a hunch I checked the main linux logs at /var/log/messages and found that my new 1.5 Terrabyte sata hard drive was being reset while the skipping happened. I changed the power cable and the ports of the hard drive, having read, that my trusty GigaByte motherboard hat issues with some ports. Nothing changed. I thought about sending the harddrive back, but then found a forum that had hundreds of posts describing similar problems under Windows XP. Some claimed that a new firmware by Seagate fixed the problem. I downloaded the CD-ROM image and after a reboot it was done. No more skipping.
The debugging output was as follows:
Dec 16 20:38:15 elkin kernel: [852826.062527] res 40/00:00:00:00:00/00:00:00:00:00/00 Emask 0x4 (timeout)
Dec 16 20:38:20 elkin kernel: [852831.093086] ata5: port is slow to respond, please be patient (Status 0xd0)
Dec 16 20:38:25 elkin kernel: [852836.067813] ata5: device not ready (errno=-16), forcing hardreset
Dec 16 20:38:25 elkin kernel: [852836.067818] ata5: soft resetting link
Dec 16 20:38:26 elkin kernel: [852836.319820] ata5.00: configured for UDMA/133
Dec 16 20:38:26 elkin kernel: [852836.319831] ata5: EH complete
Dec 16 20:38:26 elkin kernel: [852836.320232] sd 4:0:0:0: [sdc] 2930275055 512-byte hardware sectors (1500301 MB)
Dec 16 20:38:26 elkin kernel: [852836.340362] sd 4:0:0:0: [sdc] Write Protect is off
Dec 16 20:38:26 elkin kernel: [852836.357920] sd 4:0:0:0: [sdc] Write cache: enabled, read cache: enabled, doesn't support DPO or FUA
Just in case you have similar issues with your drive, mine is called ST31500341AS. The required firmware file is called ST31500341AS_SD1A.zip, search for it on google, as it is not officialy available from Seagate.