I solved my issue with my 9800GT by using NVenabler64.kext.
Firstly, I deleted networkpreferences.plist from the system preferences folder.
then deleted all the network controllers from preference, network.
Reboot.
Install network controllers from the same panel, ethernet first, then WIFI.
Reboot.
This made the app store & iCloud work properly with no "cannot verify" error.
Then I used the next installer bundled with multi beast lion to install NVEnabler64.kext.
Reboot.
Solved
Hope this helps someone.
