works fine for me on my MBP C2D running 10.5.5... I even was able to share my connection to my wife's MB, everything ran fine... WEP and all...
What version of wmwifirouter are you running? I believe I have 1.2... the only thing I have to do sometimes is turn airport off/on and then I might have to click on the ad-hoc connection "wmwifirouter" a few times as well.
I cannot thing of a single thing I changed in wmwifirouter (didn't know what to change because the documentation isn't out for 1.2 yet!), but I did switch the connection from PAM to Sprint PCS.
Hope this helps.
