Signal issues

[mforest]

Hi
I'm using Mythbuntu, currently on V 10.04 and in the process of upgrading to 12.04.
Regardless of what kernel version I use, I frequently have signal issues. When connecting to a tv channel, I may get a good picture for a few seconds and then it turns in to block and then eventually totally goes to custard with a mythtv error message. Most of the time, I can not even get a lock.
I have a script that will stop mythtv backend, rmmod the driver and then modprobe the driver and start mythtvbackend. I normally have to do this up to 30 times until I get the tuner card to work.
I have tried lots of different kernels, drivers and firmware versions. I have also tried various module parameter alternatives as per the readme file. Based on what I hear from other people, the card should be rock solid!
Any suggestions?
Cheers
Martin