I have a very similar problem. I got my DriveKey on Tuesday and installed it that night.....burnt some games (pal on a pal system) on Wednesday and they worked fine. Tried to play them on Thursday and the Wii would not read them.
Tried again on Friday night and the Wii would read them. Started to play COD and got 10 minutes in when the Wii said that it could not read the game.
Am using Memorex DVD-R and burnt at 2x on Imgburn.
Was going to get some Verbatim DVD -R today as I had read that they were best but not sure now.
I am on 4.2E
Original games work at all times.