This is the second time this has happened now.
Once in my E39 Touring, and now in the X5.
Both had pixels out in the gauge cluster and the MID.
Both clusters worked fine as soon as I put double-DIN head units in the cars (removing the MID in the process).
I didn't think that removing the MID had anything to do with it when I did the install a few years back, but I started the X5 for the first time tonight since the install, and the pixels were perfect (they were almost completely illegible before).
Unless it's pure coincidence, my guess is the voltage is fed to both displays on one circuit, and removing the draw from one compensates for the poor ribbon connection (this is purely a guess).