As I can see, one can solve this problem on earlier versions of ubuntu. But there is no packages for raring in ppa:markus-tisoft/rt3090 and it doesn't compile from sources. Also, there is no rt2860sta.ko and rt3090sta.ko in ubuntu repositories other than for lucid. Have they discontinued support for this device? I can probably use old kernel, but I'd like to find a better solution if any.
Please be sure the hardware switch is set to enable the wireless radio. Also detach the ethernet cable so that Network Manager will activate the wireless.