i have the horizontal lines. Specifically, i have: late 2006 white core 2 duo imac with isight built in. radeon x1600 video card. horizontal lines, random lock ups, and all sorts of crappy computing experiences... so i have been reading the apple support forums and as ive mentioned there it seems to me that this HAS to be a driver issue and not a logic board issue... if it is a logic board issue it must not have anything to do with the actual video card, and i think it is an os x issue because: 1) this problem did NOT exist before leopard existed (all users complain that this happens after 10.5.0 launched 2) the problem gets less bad after each new point release (i for example wasnt even able to use my mac without a complete video lock up until after 10.5.whatever came out after the initial release 3) the problem hits all sorts of video card types, both nvidia and ati so seems that this problem could be solved by a new driver or a completely new logic board. the apple store genius i cornered admitted that he MAY be able to replace the entire thing for free, but did nor promise anything (50/50 chance he said) but ive read that this happens again after the replacement for many folks. ive also heard that beta versions of 10.6 do NOT HAVE THIS PROBLEM. smc fan control does nothing to stop it after a little while, the problems come back no matter how cool the system is running. so will they fix for free? what do you think, and do you have any suggestions for me before i bring it in? installing 10.5.7 now. lets hope and see.