Random characters in Outlook 2003 client

[Paul]

I have a client running Outlook 2003 on XPSP2 who is complaining about
random erroneous characters appearing in her Outlook text when she composes
messages. The characters have also appeared randomly in her signature file.
Here is an example:

Tel: 123.456.7890 ââ?"ª Fax: 123.456.7890

Date:Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â
  Wednesday 16th May

Time:Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â
 2:00pm

Approximate duration:Â Â Â Â Â Â Â Â Â Â Â 30 â?" 45 minutes

The problem has been getting worse. Does anybody have any idea what could be
causing this ?? This is a US-based PC using US English, so I have no idea
where these characters are coming from.

Thanks in advance.

Paul