customising the select and setting an alternative web safe font ('Droid Sans') resolves the display corruption, and doesn't require the hack.
I could investigate whether there is a problem with my font-face files, however I'm not certain where to start.
When happens when you use Droid Sans through @font-face, instead of just using the Google-hosted version? Do you experience similar issues?
I would like to know if the problem is caused by @font-face, or by the font you use.