The relevant error in the mongrel log is:
** Starting Rails with production environment...
/usr/local/lib/ruby/site_ruby/1.8/rubygems.rb:319:in `activate': can't activate rubyforge (>= 1.0.0), already activated rubyforge-0.4.5] (Gem::Exception)
from /usr/local/lib/ruby/site_ruby/1.8/rubygems.rb:337:in `activate'
from /usr/local/lib/ruby/site_ruby/1.8/rubygems.rb:336:in `each'
from /usr/local/lib/ruby/site_ruby/1.8/rubygems.rb:336:in `activate'
from /usr/local/lib/ruby/site_ruby/1.8/rubygems.rb:337:in `activate'
from /usr/local/lib/ruby/site_ruby/1.8/rubygems.rb:336:in `each'
from /usr/local/lib/ruby/site_ruby/1.8/rubygems.rb:336:in `activate'
from /usr/local/lib/ruby/site_ruby/1.8/rubygems.rb:337:in `activate'
from /usr/local/lib/ruby/site_ruby/1.8/rubygems.rb:336:in `each'
... 33 levels...
from /usr/local/lib/ruby/gems/1.8/gems/mongrel-1.1.5/bin/../lib/mongrel/command.rb:212:in `run'
from /usr/local/lib/ruby/gems/1.8/gems/mongrel-1.1.5/bin/mongrel_rails:281
from /usr/local/bin/mongrel_rails:19:in `load'
from /usr/local/bin/mongrel_rails:19
The app still uses Rails 1.2.3 per the RAILS_GEM_VERSION = '1.2.3' unless defined? RAILS_GEM_VERSION
line in environment.rb. I'm embarrassed to say I haven't frozen rails as all good advice suggests, but it hasn't been a problem and I had good intentions to upgrade to Rails 2.x "any time now".
I do have several gems in Vendor (Gruff, PDFWriter, and Sparklines), but RMagick is not there (should it be?)
I can't find any specific relevant threads in this forum, but a wider search turns up a few ideas, mostly involving uninstalling rubyforge--which I presume doesn't apply in shared hosting.
Any ideas for both quick-fixes (I really need to get it back up ASAP) and longer term strategies are welcome.