Today I rebooted my system and for some reason the menu at the top is blank... no global menu, no time, no date, no nothing...
Do you have any idea how this can be rectified?
This can happen if you've changed some Compiz settings which have messed up Unity. You can reset Unity to its default settings.
Hit Alt+F2 and run the following command:
This will only reset the Unity settings in CompizConfig Settings Manager and leave the other CCSM settings intact.