I have exactly the same issue with ZoneFlex R600 access points. If a particular SSID lies in a VLAN, Linux and Mac machines are unable to get IP addresses. DHCP Offers never make it to the access point. Windows machines (that includes Windows Phone) are able to get the Offers, send Requests and get Acks.
I'm sure this is not my network infrastructure/dhcp server/dhcp relay issue, because when I plug a Linux machine with a patchcord to the switch port dedicated for the VLAN, it is able to get an address.
We got 9 access points a week ago and this problem prevents us from installing them in our office, since 90% of client devices are Linux/Mac. This is crazy!
Ruckus, if you do a packet capture you will see that Linux/Mac machines send a slightly different DHCP Discover than Windows machines. Linux/Mac have the Broadcast flag set to Unicast, while Windows sends out packets with the Broadcast flag set to Broadcast. Perhaps this is the problem.
I'm expecting a quick fix, or else we're returning these devices.