if you were able to had your 5+ GPUs running in one rig with win7 64bit then you must have used the modded inf files afaik.
i believe that this was the thread i got the modded *.inf files from: https://litecointalk.org/index.php?topic=11761.0
it says that it ONLY works wit 13.12, but i swear i just installed the 14.6rc2 Drivers, used the modded inf, and all GPUs get detected.
Indeed , I Installed 14.6 RC2 , and one of the cards was with an error on the device manager. After that downloaded the 13.12 drvs from techpowerup , and just ipdated the damaged card with 13.12 ver of the driver and now its fixed , 5x280X GPUs on 4.277 MH /s on X11
wait... so which version of the miner are you using and what modifications in files did you have to do to it to be able to run x11? I finally got my rig to read 6 cards again after fiddling with it all day long trying to upgrade to the new djm34 miner... but it ended in not detecting all my cards.
wasted all day. now I finally detect all cards but hashrate is the same as before