More details: If I go into Start>Control Panel>Printers and Faxes and select the local (Canon) printer and set it as the default, it indeed gets set as the default printer in all applications as long as I am logged on.
Once I log off (i.e., shut the computer) and re-start, a network printer (Epson) gets reset as the default printer. So, I have to switch the default printer setting back each time I logon.
[#0005ff]Sounds as though it could be a Group Policy but it's worth looking in System Configuration to see if it's something that starts up when you boot. Go Start>Run type msconfig into the open box and hit Enter. Look under the StartUp tab for anything Epson printer related and untick it.