I have the Lexmark CX317DN connected to my network and was having the same problem. This may work for other Lexmark printers (or other brands), but I haven't had to try. The "Generic Postscript" workaround allowed me to print, however I lost some functionality such as two-sided printing. My solution that has worked (so far) is as follows:
1) Find the IP address of the printer on the network (mine is 192.168.1.120, yours is probably different)
2) Open System Preferences -> Printers & Scanners, and click the "+" to add a printer
3) Click the globe in the center near the top
4) Type the IP address of the printer in the "Address" field (mine is 192.168.1.120, yours is probably different)
5) In the "Protocol" field, select "AirPrint"
6) In the "Use" field, select "AirPrint"
7) Name the printer whatever you'd like
8) Click the "Add" button
9) See if it works
Keep in mind, this will probably only work if your printer is connected directly to your network. To find the IP address, open the printer web page by clicking the "Options & Supplies..." button and then clicking the "Show Printer Web Page..." button. The address should be listed at the top of the page:
If it isn't, while looking at the printer web page, click on "Settings" on the left:
then click on "Network/Ports" under "Other Settings":
then click on "TCP/IP":
and the address should be the third thing listed:
If you're comfortable adjusting your router settings, while you're there, it might be a good idea to click "Set static IP address" and then click "Submit", and then adjust the settings on your router to reserve that address for your printer. That (should) prevent the address from changing in the future and you having to repeat this whole process.