I've been successfully running GEM on 11.10 64-bit for a while now. What I had to do was install the old versions of the required libraries from the 10.04 repository. You'll have to install a series of packages, but I can't remember exactly which ones (the console window will tell you what you need, there are a few more after quicktime1). You can find the 10.04 versions in Ubuntu's package repository here.

http://packages.ubuntu.com/

just wanted to let people know that I found a solution to this problem. You just need to download the lucid versions of libmagickcore2, libmagickwand2, and libmagick++2, then GEM should work on maverick 64-bit.