Did you configure the Airport express printing capability? -- its on the airport express configuration page (Airport Admin Utility)
and of course, you might want to read the help file or the manual.
I have an Epson RX700 printer connected to an Airport Express base station. I can print from my Mac (20" iMac G5 1.8Ghz, OS X 10.4.4, Airport Extreme card), but not from my PC (2.6 Ghz P4, Windows XP Home) on the same wireless network (PC has Netgear card).
When I send a print job from the PC I don't get any error messages - the driver status window shows that the job was sent, but the printer doesn't respond.
I used Bonjour to on the PC side to set up the printer.
File sharing and internet access seem to be working fine.
Any ideas?

Chowhound
Comic Vine
GameFAQs
GameSpot
Giant Bomb
TechRepublic