User-agent: Mozilla/5.0
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:
http://kmeleon.sourceforge.net/forum/read.php?3,100751
Bug 1177 - "Printer error: not available" is showed to open a 2nd Print dialog instance from toolbar.