Over the weekend, we found out from our excellent community that the attributes improvements weren't totally backwards compatible as we thought.
For now the 0.7.6 gems have been pulled from [deprecated location]* and we will be releasing Chef 0.7.8 later today which will fix the issues. Summary of the attributes-related issues:
Full notes about the release will be posted when 0.7.8 is available.
*Note: since the original date of this post, Chef gems have been updated to be distributed through rubygems.org.