I recently upgraded a server from Ubuntu 8.04 to 10.04, and it seems to have broken RMagick, with this error:
libWand.so.10: cannot open shared object file: No such file or directory - /opt/ruby-enterprise-1.8.7-2009.10/lib/ruby/gems/1.8/gems/rmagick-2.12.2/lib/RMagick2.so
Poking around the web for ideas, I decided to try symlinking this to libMagickCore.so.2.0.1, and libWand.so.10 to libMagickWand.so.2.0.1. That got me a new error:
This installation of RMagick was configured with ImageMagick 6.3.7 but ImageMagick 6.5.7-8 is in use.
Since then I've been trying all sorts of googling and uninstalling and reinstalling of RMagick and the various ImageMagick libraries and having no luck. I think some libraries may have built from source or otherwise "manually" installed by previous staff.
---(added later:)
It appears that RMagick 2.13.0 or 2.13.1 has been fixed to work with ImageMagick 6.5.7, but when I try to specify one of those versions to gem install, it either: (a) appears to install, but only 2.12.2 shows up in 'gem list' and only 2.12.2 is loaded by my rails app; (b) errors "ERROR: Could not find a valid gem 'rmagick' (= 2.13.0) in any repository" if I specify 2.13.0. "gem -v" says 1.3.5.
---(and later:)
Updating RUbyGems to 1.3.7 as described here: http://wiki.joyent.com/all-accelerators:kb:rubygems hasn't changed anything.