[imp] charset="iso-8859-1" wont display body of message inline

[Michael Bellears]

Just recently upgraded to Horde 3.0.7 + Imp 4.0.4, and we connect via
Imap to a clients server to provide them with Webmail Access - It seems
as if there Exchange Server formats there messages in iso-8859-1 and Imp
cannot display the body of the message inline - We get an "unnamed
[text/html]" which if clicked, displays the body of the e-mail
correctly.
Viewing message source shows:
Content-Type: text/html;
	charset="iso-8859-1"

We also have an Imap connection to our Exchange server which works fine
(Message body is correctly displayed inline) - Viewing message source
shows:
Content-Type: text/plain;
	charset="us-ascii"

We run Debian 3.1, so assumed it was just a prob with a missing
ISO-8859-1 locale, so I performed a dpkg-reconfig locales, and added
support:

Generating locales...

  en_AU.ISO-8859-1... done
  en_AU.UTF-8... done
  en_US.ISO-8859-1... done
  en_US.ISO-8859-15... done
  en_US.UTF-8... done
Generation complete.

Restarted Apache, but the message bodies are still not being displayed
inline for the clients mail?

Any suggestions are greatly appreciated.

Horde Version
Horde: 3.0.7
Horde Applications
Horde: 3.0.7
Imp: H3 (4.0.4) (run Imp tests)
Turba: H3 (2.0.4) (run Turba tests)
PHP Version
View phpinfo() screen
View loaded extensions
PHP Version: 4.3.10-16
PHP Major Version: 4.3
PHP Minor Version: 10
PHP Subminor Version: 16
PHP Version Classification: release
You are running a supported version of PHP. 

Regards,
MB