iPad printing is unreasonably difficult. It all works fine no doubt if you go out and buy a shiny new AirPrint enabled printer. Otherwise the simplest/cheapest thing I've found is:
- AirPrint Activator v2 is free/donation-ware for Mac OS X at http://netputing.com/airprintactivator/airprint-activator-v2-0/ which exposes your built-in printer sharing over airprint.
I've had network problems too, similar to the problems with iTunes. Replacing my router was the best solution I had for that. If your router is old, or a very cheap broadband freebie, you may need to replace it.