I was a bit puzzled why my printing stopped working and would essentially freeze the application I was trying to print from. I had 3 printers in my settings, One Windows shared HP7960, one HP 7960 that appeared when I directly plugged my MacBook Pro into it and another older HP that I plugged directly in the MacBook Pro that didn't work properly. When I opened up Printers under System Preferences it shows all three printers being Idle and w/ a green light even though 2 of them were not. I was not able to rearrange preference order. Once I removed the two phantom printers, I was able to print to my HP7960 Windows XP shared printer via the Gutenprint 7550 driver.
So in the course of trouble-shooting printing issues, especially networked printers, make sure only one printer is in the list.