"Printer not connected; will retry in 30 seconds..."

[Roger Morgan]

I made a little progress with this (no solution, though). There is a post by someone who saw a similar problem at:

http://www.mail-archive.com/linux-il@cs.huji.ac.il/msg44505.html

which suggests it has something to do with locale settings. The output of locale on my system is:
LANG=
LC_CTYPE="POSIX"
LC_NUMERIC="POSIX"
LC_TIME="POSIX"
LC_COLLATE="POSIX"
LC_MONETARY="POSIX"
LC_MESSAGES="POSIX"
LC_PAPER="POSIX"
LC_NAME="POSIX"
LC_ADDRESS="POSIX"
LC_TELEPHONE="POSIX"
LC_MEASUREMENT="POSIX"
LC_IDENTIFICATION="POSIX"
LC_ALL=
i.e. I am using the default, C, locale. But if you look at the cups error log in the parent message, there are references to the en_US locale, and when I searched the error log I found this:
---extract from /var/log/cups/error_log
D [15/Jul/2006:10:54:11 +0200] [CGI] perl: warning: Setting locale failed.
D [15/Jul/2006:10:54:11 +0200] [CGI] perl: warning: Please check that your locale settings:
D [15/Jul/2006:10:54:11 +0200] [CGI] LANGUAGE = (unset),
D [15/Jul/2006:10:54:11 +0200] [CGI] LC_ALL = (unset),
D [15/Jul/2006:10:54:11 +0200] [CGI] LANG = "en_US.UTF-8"
D [15/Jul/2006:10:54:11 +0200] [CGI] are supported and installed on your system.
D [15/Jul/2006:10:54:11 +0200] [CGI] perl: warning: Falling back to the standard locale ("C").
---end extract
Now, it's just a warning, so it shouldn't matter, right? Hmmm.
But why does cups make the assumption that I want to use en_US.UTF-8?
What is there about CUPS that prevents it from working in the default C locale?
Assuming that CUPS has a bug which prevents it working if the locale of the user trying to print is the default C locale - how do I work around it?