I too was having problems trying to get my Samsung CLP-510 to print wirelessly from an Airport Express Base Station from two different MBPs - one using Tiger and the other using Leopard. Here are the solutions that worked flawlessly for me.
For the Tiger MBP:
1. Uninstall printer
2. Download and install latest drivers from Samsung at
http://www.samsung.com/us/support/download/supportDown.do?modelnm=CLP-510&mType=DR&vType=L&dispnm=CLP-510
Note: If you're not using the CLP 510, simply search for your model number in the search box. You will be directed to a page for downloading the drivers for your operating system.
3. Reinstall printer
4. Print - It worked perfectly for me after I tried everything.
For Leopard: This should work with any printer problems that occur after updating to 10.5.2. I found this solution on another discussion board and it was posted by Bill Helsabeck
1. Add Airport printer
2. Download this utility:
http://ftp.easysw.com/pub/cups/contrib/FixAirportPrinter.dmg
3. Run FixAirportPrinter application
4. Double-click on printer in list (or click on printer and click on
"Fix Printer" button)
Good luck!