What chatwindow style are you using.
What happen if you change the style.
also make sure you haven't disabled theses effect  (overide user ...  in the chatwindow appareance tab)

CVS commit by ogoffart: 

Fix Bug 100577: kopete does not show custom font colour, font size or font attributes, e.g. underline, bold... (in a MSN conversation)

BUG: 100577


  M +2 -2      msnswitchboardsocket.cpp   1.117


--- kdenetwork/kopete/protocols/msn/msnswitchboardsocket.cpp  #1.116:1.117
@@ -251,5 +251,5 @@ void MSNSwitchBoardSocket::slotReadMessa
                         QString color;
 
-                        rx=QRegExp("X-MMS-IM-Format: ([A-Za-z0-9$!*/;\\-]*)");
+                        rx=QRegExp("X-MMS-IM-Format: ([^\r\n]*)");
                         rx.search(msg);
                         fontInfo =rx.cap(1);

is this done in version of kde 4.0 final of today?

I hope so ;)

thanks anyway!

No, the commit came too late. This bugfix isn't included in the Kopete released
today.

By the way, that was KDE 3.4 that was released, not 4.0. You won't see 4.0 for
another year.

The bugfix will be present in 3.4.1.

ohh sorry... of course I meant 3.4. But I'm looking forward to the 4.0 version.
Thanks for fixing it. Probably I'll use a cvs version to have it fixed. 

*** Bug 103915 has been marked as a duplicate of this bug. ***

Thanks again Olivier !
You've made my girl friend happy ;)
:D