I recently encountered an issue with a network printer that was rather perplexing. I did not readily come to the correction until I had put some time into it.
Here was the situation:
We have a network printer that I added to my machine via the admin/printing section in ubuntu. I listed the printer in the network section, so I selected it and then hit apply. It created the printer and I could print a test page, but anytime that I tried to print any other kind of document to it, the printer always told me that there was no connection to it.
I finally removed the printer, copied the IP that it saw in the network listing for the printer and used the HP Jetdirect option instead of letting ubuntu install from the list of printers. Now even though its not using a Jetdirect, I entered the IP address and left the default port and it now is allowing me to send my print jobs to it.
So the final verdict is:
If you have a network printer that is not attached to a machine, IE: the printer has its own printer ip, then use the Jetdirect option instead of letting ubuntu install the drivers.
After 11 years of working for the same company I was laid off today. I find it interesting that 2 hours after I posted this I was unemployed for 9 months.