The order of arguments in one of the dbus_g_proxy_call invocations in
dbus-viewer.c is wrong.  Here is the patch:

Index: dbus-viewer.c
===================================================================
RCS file: /cvs/dbus/dbus/tools/dbus-viewer.c,v
retrieving revision 1.14
diff -u -c -r1.14 dbus-viewer.c
cvs diff: conflicting specifications of output style
*** dbus-viewer.c	6 Jul 2005 21:27:45 -0000	1.14
--- dbus-viewer.c	30 Jul 2005 14:55:56 -0000
***************
*** 182,189 ****
          }
    
        if (!dbus_g_proxy_call (proxy, "Introspect", error,
- 			      G_TYPE_STRING, &data,
  			      G_TYPE_INVALID,
  			      G_TYPE_INVALID))
  	  goto done;
        
--- 182,189 ----
          }
    
        if (!dbus_g_proxy_call (proxy, "Introspect", error,
  			      G_TYPE_INVALID,
+ 			      G_TYPE_STRING, &data,
  			      G_TYPE_INVALID))
  	  goto done;