if you don't have the lastest firmware for the wiikey, try switch back the wii drives and update the wiikey.
I don't know if the firmware within the drivekey is updatable, but if it is, check for an updated version!
Either:
* the update is infact completed and you can play joyfully.
* you'll brick it. corrupted files. have nand backup with bootmii?
* you'll brick it. boot2 is overwritten with the update. install bootmii (again)
* you can reinitiate the upgrade to 4.2. (hopefully this is the case)...
raptir, the easiest way is to install the wiiware or vc with the help of showmiiwads on the pc. on the wii, launch triiforce or "triiforce mrc" and you can play most of the games. a few doesn't work, like orbient.
look for guides.