Mac OSX: Tiny toolbar Icons

I'm on Mac OSX. Version info:
[quote]
[523] bzr version
Bazaar (bzr) 2.1.0
  Python interpreter: /usr/bin/python 2.6.1
  Python standard library: /System/Library/Frameworks/Python.framework/Versions/2.6/lib/python2.6
  Platform: Darwin-10.2.0-i386-64bit
  bzrlib: /Library/Python/2.6/site-packages/bzrlib

[524] bzr plugins
...
explorer 1.1.0dev
    Version Control for Human Beings.
[/quote]

When executing bzr explorer and giving it a branch location the toolbar icons appear tiny (see attachment).
[source]
cd [local branch]
bzr explorer .
[/source]

If I don't supply a location:
[source]
cd [local branch]
bzr explorer
[/source]

The toolbar icons show up fine.