xul rendering mozilla 1.7

i have an xul application that used to work quite fast on mozilla 1.6. When
i open the application in mozilla 1.7, i notice that all actions are
noticable slower, i mean, when i push a select list button, the select list
doesn't open as smootly as it did in mozilla 1.6. the same thing for the
tabs of tabpanel.
in fact, the mozilla menus seem to very slow as well. when i traverse the
menus horizontally, the old menu is still there when the new menu appears
on top of it. my hardware is an amd athlon 1 Ghz, and running suse 9.1 on
ity. 


jef