Start menu tab not working

[XP User]

Hi all,
I have Windows XP Professional installed on my laptop.
For some reason all of a sudden my start menu tab stopped
working. If I click on the "Start" tab, I do not get the
menu I usually get.

I customised my XP to have the classic Start menu. If I
use the normal XP Start menu, I do get the menu popped up
but If I pause my mouse on All Programs link, I do not see
the programs showing up.

If anybody can suggest a solution for this problem, it
will be really helpful.

Thanks.