I have been attempting this on and off since 10.10 RC1. The machine I use also has a Belkin N Wirelss card using the Ralink 2860 chipset.
The result of compilig the 3090 driver from the Ralink website has always been for the computer to hang at the logon screen but now its working.
Attached below is the correct driver from the Ralink Website. Download Ralink Driver file, extract to a folder and edit the file in
HAS_ATE,HAS_WPA_SUPPLICANT, HAS_NATIVE_WPA_SUPPLICANT_SUPPORT,HAS_ANTENNA_DIVERSITY_SUPPORT from =N to =Y.
If you have not allready done so install the requirements to compile the driver. Specifically sudo apt-get install build-essential devscripts cdbs.
In the DPO_RT3390_LinuxSTA_V22.214.171.124_20100831 directory run sudo make and then sudo make install.
Restart your machine and you should have a device ra0 showing in ifconfig. lsmod should show rt3390sta. If not then edit /etc/modprobe.d/blacklist.conf and blacklist the items shown below. I had to include the rt3090sta and rt2860sta which were drivers from previous driver compilations.