There might just be an easier solution.

We found out that ThinPrint (as stated by someone else) tries to set the default printer every time you log into View.

There is a registry key that disables this behaviour without doing other stuff that might damage printing.

Try to add (it doesn't exist by default) the following key

HKLM\Software\ThinPrint\TPAutoConnect\DisableSettingOfDefPrinter=1 (DWORD)