Yeah that's the one problem with the way OpenAL is setup under Windows. It was done to allow easier use of protected technologies by the hardware manufacturers but it means about 3 different dlls will be in use for OpenAL: a router, a wrapper, and a native dll. It's only the native dlls that you have to really be careful of so if you are using NVIDIA drivers (for an nforce boad) then make sure you don't have "ct_oal.dll" since that's the Creative native dll. If you have Creative drivers (what is linked from the OpenAL site or for your sound card) then you have to make sure you don't have "nvopenal.dll" in there.
Unfortunately even the newer sound code I'm working on can't fix (or deal with) this problem automatically so there will continue to be a problem when you are switching between the various custom drivers (Creative, NVIDIA, etc.). The situation is a lot cleaner and simpler on Linux and OS X, which is rather strange given the history of everything.
We will start making full use of the native DLLs before too long though. That will open up better performance and more features (EAX, full hardware acceleration, etc.) but for now it's still using the basic sound device with FS2_Open.
