I don't know how it suddenly became this but here's what's happening right now:
e.g. I have 2 firefox windows open, so I see 2 small arrows on the left side icon of the unity launcher. Before, when I click on the firefox icon, I see 2 small windows of the firefox so I can choose which one. Now it suddenly stopped working. (super+W still works though). The bug on my system applies to all progams with multiple window instances like nautilus, terminal, etc.
Please help, I don't know what to do. I also have cairo dock, compiz, myunity installed in my 12.04. I tried searching online to no avail.