I'm using VirtualBox on Windows to run an Ubuntu OS, which is running the turnkey rails package, which comes with ruby 1.8, rails 2.3.8, and passenger 2.2.5. When I first booted it up with just a vanilla rails app it worked fine, but now I'm getting the following error:

uninitialized constant PhusionPassenger::Utils::PseudoIO::StringIO

I googled this, and on the phusion/google groups it said this was an old error and to upgrade passenger, which I did with gem upgrade passenger. It said it was installing passenger 2.2.15, but it doesn't appear to be using it. I re-started the whole virtualbox and it is still giving me the same error, with the backtrace showing passenger-2.2.5.

I realize there are several layers here and plenty of places for things to go wrong, and to add to that, I'm pretty much a Linux newb. I've got some experience with rails. I'd appreciate any help.