This may have nothing to do with your problem, and your problem occurred over 2 years ago, but I wanted a proper thread to post my solution and this is sort-of relevant. Perhaps it will help someone.
I have a Lexmark Z1480 and was able to print wireless with OS 10.4, but no longer with OS 10.5. I won't go into the boring details, but ultimately, I went into the settings for my wireless router (D-LINK) and changed the "DHCP IP address range" from "192.168.0.100 - 192.168.0.199" to "192.168.0.2 - 192.168.0.199", and it finally worked. I noticed that, since the OS upgrade, all IP numbers on my network changed from 1 or 2 digits to 3 digits after the final period. I vaguely remember my printer's ending in one digit.
I cannot say with 100% certainty that this was the solution, but there is no other clear reason. Lexmark's troubleshooting page directed me to my router's settings, so that was a good place to start. If anyone can clarify what I did (or didn't do) more articulately, this might help.
http://support.lexmark.com/index?page=content&id=SO4472&locale=EN&userlocale=EN
Error:
Connection failed: Your printer could not connect to your wireless network.
Message was edited by: lisairis