Glad you got your problem circumvented.
Did you want it solved? You don't say if you are running OpenBSD 5.0 or -current, or perhaps something even older, nor do we know which Ralink chipset is in the device.
If you're running 5.0-release or -stable, there's been one change to if_rum.c in -current that has not been backported. It fixes a problem with 11g beacon frames. See
http://www.openbsd.org/cgi-bin/cvswe...v/usb/if_rum.c