Drop down menus broken front end!

hi SI team

I am just guessing but I think this is some kind of Java problem similar to what happened in the back end the last couple of times!

http://stackideas.com/forums/my-upgrade-button-has-disappeared-in-backend
http://stackideas.com/forums/accessing-setting-for-themes-in-es-v1-3-10

This time around I am in the front end. To the right of the main menu there is the little login box. It used to be the case that when I rolled over the full login box would pop down. This is since my last update no longer the case. Currently bang up to date. If I login by going here:
http://finalbug.net/synergise
The other menu points notifications etc also do not drop down.

thanks

Paul