Had a client with this issue – a HP 3800 driver on an SBS 2008 server printing via the network. Problem was that they were unable to change the default printer port. After some investigation it seemed like the driver was not detecting the printer correctly and specifically the trays attached.
The solution was to install the universal printer driver for pcl5 from HP which you can get from here or by googling hp universal printer driver. Once installed the driver queried the printer – after giving it the ip address it was on. The printer was then installed in control panel and when opened – the properties allow the selection of a default tray as required. Removed the less functional printer and driver to prevent future confusion.