[jQuery] SuperFish with supersubs problem

[Karol Rybak]

Hello, I have used superfish & supersubs on that website 
http://www.atut.lublin.pl/
it works great in ie, however it's got problems in firefox 3. When i
first enter the site (empty cache) measuring does not work well and
submenu MIERZONE GAZY is much too wide. When I enter a different page
(cache primed) everything is ok. I tried debugging with firebug or
displaying alerts, however when i do that it works fine everytime.
Anyone have an idea what is wrong ?