Following popular demand the new kernel set ships with RaLink legacy wlan modules in addition to mac80211/ rt2x00 again, to prevent race conditions between both drivers the rt2x00 variants need to be blacklisted if you intend to install the legacy drivers. A new udev-config-sidux version takes care of that (apt-get update; apt-get install udev-config-sidux), if you intend to keep the rt2x00 drivers (recommended), you need to remove that blacklisting once (rm /etc/modprobe.d/mac80211).

For further background information, please take a look at Kernel ≥2.6.21.1*-4 and mac80211.