Mailer template names and underscores weirdness

Recently, in one of my projects that mailers stopped working.

It was complaining that it couldn't find a rhtml, rjs, etc.. file.

by looking at the stack trace, it appears to be appending an underscore to the file name it's looking for.

So if I have a mailer method named contact, it's looking for the file contact_.rhtml. If I just have contact.rhtml, it blows up.

Has anybody else seen this behavior, or know what's causing it.