Weird Closing Issue for Files

I am experiencing a problem where my excel seems to have frozen with four files remaining open. I can put my mouse in a cell and manually type something, but am unable to select anything via the menu bars using a mouse. I am in a server, so CNTRL ALT DEL doesn't work. When I manually try to close the file using ALT F4, it tells me "Cannot Quit Microsoft Excel" and shows the help menu. I've looked at all the options and nothing really applies. Can anyone help.

Teeni