Hi,
I got the same problem a few days ago (
http://groups.google.com/group/
haml/browse_thread/thread/9a1cc4868ab12c72).
I was unable to recreate a minimal Rails app that demonstrates the
issue, as suggested by Nathan (maybe you could).
The cause of this issue is probably the presence of non Rails3-ready
gem (or several).
Which version of the haml gem do you use?
I finally regenerated a blank rails 3.0.0.beta4 app, used haml
(3.0.10) and copied all the files I needed in it, and it worked. Not
so elegant for a solution but I'm still investigating the cause of
this issue (probably the devise gem in my case).
Best,
Yannis