Try creating a separate printer on the server with the Windows 7 driver so all the XP machines can still work fine. That way you would have 1 printer for XP and 1 for Windows 7. Try changing the drivers on the windows 7 printer until you get your required results. Then test the XP clients on the same one and see if it works. If not you could stay with the 2 printers for either OS.
The issue will probably be down to the driver so keep trying the alternative on the ricoh website. For example try the PCL 6 Driver Ver.1.2.0.0 and PCL 5e Driver Ver.1.2.0.0.