I know this is already an old thread, but I believe the information might prove useful to those who own DLINK DP-301U.
Below are the steps I took in order to print successfully.
Printer Make: HP
Printer Model: p2015d
OS: Ubuntu 10.10
Wireless Printer Server: DP-301U
1. I connect to the printer directly using usb cable. I did this in order for the printer driver to be automatically installed.
2. After the driver has been installed, go to SYSTEM -> Administration -> Printing, Properties of the installed driver.
3. Device URI, Change
4. Find Network Printer, enter the IP of your Dlink.
5. I choose the 1st option LPD/lp.
That should work now.
Though if you nmap the wireless printer server,
Starting Nmap 5.21 at 2010-11-22 14:33 WIT
Nmap scan report for 192.168.3.104
Host is up (0.029s latency).
Not shown: 994 closed ports
PORT STATE SERVICE
21/tcp open ftp
23/tcp open telnet
80/tcp open http
139/tcp open netbios-ssn
515/tcp open printer
9100/tcp open jetdirect
The jetdirect option is available, but somehow under Ubuntu it doesn't seems to work. Though my last installation of Kubuntu 10.10, it works perfectly.
Hope that helps