XTEST fails to send mouse event

Hi everybody,
I think this question is for XTEST experts.

I'm using XTestFakeButtonEvent(args)
and pass there some numbers like 1, 2, 3, 4, 5. That works fine everywhere.
But once I tried to pass 6 and 7 in then it just work silently and no 
event is actually happen.
That happens on Suse9.3.

Furthermore, I have another Linux (ubuntu6.06) installation on the same 
machine and XTEST works fine there with 6 and 7 buttons.
BTW, in both cases XTestQueryExtension(args) returns the same version : 
2(both minor and major).

If this is a know problem? How could I deal with it?
I'm looking on XTest.c source to get the answer why BUTTON6, 7, etc. are 
not posted to the system with
XTestFakeButtonEvent(params)
(got XTest source from here:
http://www.cs.wisc.edu/~vg/cgi-bin/lxr/http/source/lib/Xtst/XTest.c#L195 )

Seem it just uses xorg API:
http://www.codase.com/search/relation?namec=xtestfakeinputreq
But its not very clear what happens next in there.
There is no any responses on my question on x.org though.

Does anybody could clarify that a little?
I also should say that my mouse successfully generates all mouse events 
if I use it manually. The problem is only with XTestFakeButtonEvent.
Kind regards,
 --Andrei