Errors generating guides

Some people at the irc channel are reporting guides not being
generated, and in fact they're blank:

I've also seen that after the latest commits, I'm unable to "rake
generate_guides" on my machine. I've tried on ruby 1.8.6, 1.8.7 and
1.9.1 and I'm getting different errors. I'm not sure where the problem
can be, any idea?

Thank you Jaime, it is fixed now and edge guides are back online.

-- fxn

PS: As of this writing 1.8.6 and 1.9.1 are unsupported, Rails do not
even boot on them (by software, it is an explicit abort call) no need
to test stuff against those Ruby versions.