Sonotrode calculator & Mozilla

Hi Chris,
I am using Mozilla 1.7.2. on w2k.
The sonotrode calculator doesn't seem to work properly with my mozilla.
When I click on a top level menu (for example Material) I can see the menu, but If I try to click on a sub-menu (for example MaterialAluminium) nothing happens (the sub-menu doesn't appear).
Could you try to solve this problem?

Ciao Valerio.