I use the printer attached to my main pc, a HP Photosmart, for printing stuff from my laptop which is on a wireless network.The last time I tried to print stuff out, it didn't work. I went into the properties for the printer and ticked the box for sharing it, which had somehow become unticked.
What happens now is that the network printer keeps setting itself as the default printer on the main pc, even sometimes a few times within a session on the computer. What then happens is that when i click on the printer icon in a program, the print job fails and I have to go into the printer folder to reset my HP as the default printer. How do I get this to stick?

have you uninstall/reinstall the printer and software? see if hp has updated drivers.

I updated the driver and that seemed to fix it.