TextMate commands are only guaranteed to work with 1.8.7 (or whatever ships with OS X).
But commands use the ruby from your PATH where TM_RUBY is for user scripts, script validation and such.
So it should be safe to set TM_RUBY to a different ruby.
I don?t see any use of TM_RUBY in the GetBundles (which you mention had issues) found here: http://svn.textmate.org/trunk/Review/Bundles/GetBundles.tmbundle/ ? I believe an older version may have wrongly used TM_RUBY.

OK that makes sense.

For people referencing the archives: unchecking the TM_RUBY checkbox in the TextMate env settings got it working.

Relaunching TextMate doesn?t change the command environment, so wouldn?t think so, but I don?t know what ?using RVM to switch Rubies? conveys.

Gotcha, good to know. AFAIK RVM just switches out some symlinks similar to python_select & others, nothing that would mess with TM.

Thanks for all your help, Allan!