Maybe F5 could update all the variabes/values in the Watch window similar like we have F5 in browser to update page.
Can be done, but I have not had a case where it is needed. (It won't be a f5 or any other shortcut, just a menu item).
Probably it will be useful if you disable many watches and then want to update them at once...
Note, that most of my time (at least 35%) which I spent with using Watches I spent with manipulating/fixing the width of columns.
This is known bug I cannot reproduce reliably... so it is almost impossible to fix...
Yet I did not success to watch the array. I did as you did, but I selected the variable first and clicked on it. Then did what you told.
Just do what Jens told you and it should work, at least it has worked for me.
If it still doesn't work, you'll have to enable the full log in the settings of the debugger and then paste it in here (use pastebin like service if it is more than a couple of lines).