The error message: "Printer error: not available" is showed when you try to open a second instance of print dialog from the "Print" toolbar button.
If you try it from File menu or Print accelerator (Ctrl + P) these are disabled after the first instance is opened.
This isn't blocked/disabled in Print toolbar button.
Other browser like IE 6, for example, support to open several instances of Print dialog. Firefox 2 block the focus to Print dialog to avoid open a second instance.
I think this error message must be disabled or blocked, in this case, to avoid a bad experience for the user.
Reported in forum: