shortcut keys for merge and center in excel 2013

The only way I've been able to get back to normal is by force closing excel altogether and re-opening. If I go into the VBE, I can manually run procedures and they all work fine. I've made sure that screenupdating is turned back on at the end of every procedure. I can't think of anything in my macro that would have these kinds of effects. I don't understand what's going on at all. So if I press 's' it will input 'ss' into the cell, and then when I press enter it will auto-move to the next cell down, but nothing ends up getting saved into the previous cell. Then it gets really strange - when I have a cell highlighted and press any key to input text, it gets duplicated. BUT, if I use the keyboard arrow keys, I can see that the active cell selection moves accordingly.

When I click anywhere (trying to select a cell, or an excel menu item.clicking anywhere in excel) I'll get the a 'ding' system sound and nothing will happen. Occasionally it will run as expected but as soon as the macro ends, excel becomes unresponsive to mouse-clicks. I have a fairly lengthy macro that works perfectly most of the time. I've been having a strange problem lately. Posted this on the Ozgrid forums, but haven't gotten any help yet, so I thought I'd try here too!

Shortcut keys for merge and center in excel 2013