Yeah, RG isn't too smart about what sources it can't connect to...probably stems back to when there was only ever one source. Maybe you could take the custom one out of the .gemrc and only install custom gems with -s http://work_url ?
You can close this issue. I've discovered that you can specify
gem sources in Bundler Gemfiles. So for my work projects I use a
Gemfile that specifies our internal repository and for my personal
projects I use public sources define in .gemrc.