We noticed a problem with Anvil running on PHP version 5.1.6 due to that version's regex oddity. Most people won't have had any issues as other versions of PHP don't upset things. It even caused issues on our demo site, but wasn't noticed immediately as we've been working flat out of late and it only caused a minor formatting mess-up.
Anyway, we've updated the code and re-released the code for download. This fault doesn't affect other themes.