poor resolution connecting my MBP to TV via HDMI. visable vertical lines.

hey!

so I've been googeling around for awhile and it seems A LOT of people have this issue. but I haven't been able to find a solution yet. Story goes... connecting the MBP to the TV via DVI to HDMI gives poor resolution. the weird thing is this only happens every other time. I've tried it on my macbook pro (2007) and another macbook (2010) and it has the same issue with both (but only sometimes). any thoughts?

thanks!

Grant