I use a "Wired" Print Server, so i may be talking complete rubbish, but it seems to me that the purpose of a Wireless Print Server is to print directly from a PC with a Wireless Network Adapter installed - bear with me.
Think of the Wireless Network Adapter as a "sending" device and the Wireless Print Server as the "receiving" device. Now the problem is that your Router is also a "receiving" device and the PC's Wireless Network Adapter is "Connected" to that, not the Print Server. The Wireless Router and Wireless Print Server are both intended to communicate with a Wireless Network Adapter (i.e. they are both Wireless Access Points) and so they cannot talk directly to one another.
As I see it, a "Wireless" Print Server is only used where there isn't already a "Wireless" router involved to provide the wireless link to the PC.