[TxMt] "can't find ruby" error during svn commits

[Stan Kaufman]

While trying to do a svn commit from within TextMate, I get this error:

===
Couldn't find /usr/local/bin

We need Ruby to proceed.

Locations searched:

/Applications/TextMate.app/Contents/SharedSupport/Support/bin/CocoaDialog.app/Contents/MacOS
/usr/local/bin/
/usr/local/sbin
/bin
/sbin
/usr/bin
/usr/sbin
/usr/local/pgsql80/bin
/usr/local/pgsql81/bin
/usr/local/mysql/bin
/sw/bin
/Applications/TextMate.app/Contents/SharedSupport/Support/bin
===

A command-line svn commit within the same checkout works perfectly -- so 
I don't think that this is a svn problem.

Ruby is definitely there; the Rails app I'm developing works fine:

$ which ruby
-> /usr/local/bin//ruby

The error is particularly weird, as it clearly is looking at 
"/usr/local/bin/" when trying to find "/usr/local/bin". What can this mean?

I'm using TM build 1372 (latest), MacOS 10.4.8.

I'm guessing that this is a configuration problem, but I can't figure 
out what I've got set wrong.

Many thanks in advance for any pointers!