I had the same problem, and the culprit turned out to be the old version of "mobile fu."
I used version 0.2, and updating to version 1.1 resolved the issue for me. Version 0.2 smoothed the "stylesheet_link_tag" method in such a way that it interfered with the Sprockets :: Helpers :: RailsHelpers module. I found an offensive bit of code using grepping through all my Gems for "stylesheet_link_tag" to see where it might have been overridden.
I hope this helps anyone who encounters this problem in the future :).
source share