On another note, as I watched the clips again, I realized that when the demonstrators sang the national anthem, they were actually not using the right words. I didn't realize at the moment but when re-listening it became quite clear. It was also confirmed by this AP story on the event.
On Sunday, the protesters dispersed peacefully within an hour, singing a revised version of the Egyptian national anthem: "My country, you still have oppression in politics and economics. You need revolution, my country."
The real lyrics are: "My country, you have my love and my heart."
If you can view 3GP files (I can with Quicktime Pro for Mac OS X), click here to see that clip.