I'm using a current git version (Org-mode version 6.34trans
(release_6.34c.67.g25f76f)).

I had a quick look at the code, and it seems the problem is in
`org-agenda-align-tags'.

BTW: Is it really a good decision to propertize the text algorithmically
in the functions building the agenda?  I'm not sure, but it might be
easier to define some `org-agenda-font-lock-keywords' like it's done for
org files, too.

Bye,
Tassilo