WLM V8 - Question marks and other characters not displaying.

One of my contacts in WLM always has lots of text not showing in our
conversations... They come up in tiny little blank text boxes instead of
showing as text. The only way I can read them is to right click on the box,
copy it and paste it somewhere else where it will show normally. My contact
says that I am the only one of his contacts that has this problem.

It's always the same characters... *hehe* *!* and *?* are the most notable
culprits... Which is a shame as they are used by my contact all the time.

If I have the convo using Yahoo messenger instead of WLM at my end, the text
from this contact appears normal.

Does it mean that he is using a different version of Messenger and needs to
upgrade? If so, why is Yahoo messenger unaffected?

Any ideas?

Thanks.