package rubygems1.8 1.3.7-3 failed to install/upgrade: subprocess installed pre-removal script returned error exit status 2

I tried to autoremove rubygems1.8, and it blew up unexpectedly

ProblemType: Package
DistroRelease: Ubuntu 11.04
Package: rubygems1.8 1.3.7-3
ProcVersionSignature: Ubuntu 2.6.38-10.46-generic 2.6.38.7
Uname: Linux 2.6.38-10-generic x86_64
NonfreeKernelModules: fglrx
AptOrdering: rubygems1.8: Remove
Architecture: amd64
Date: Wed Jul 20 23:50:30 2011
DpkgTerminalLog:
 Removing rubygems1.8 ...
 update-alternatives: error: readlink(/etc/alternatives/gem) failed: Invalid argument
 dpkg: error processing rubygems1.8 (--remove):
  subprocess installed pre-removal script returned error exit status 2
ErrorMessage: subprocess installed pre-removal script returned error exit status 2
InstallationMedia: Ubuntu 11.04 "Natty Narwhal" - Release amd64 (20110427.1)
PackageArchitecture: all
SourcePackage: libgems-ruby
Title: package rubygems1.8 1.3.7-3 failed to install/upgrade: subprocess installed pre-removal script returned error exit status 2
UpgradeStatus: No upgrade log present (probably fresh install)