"Next month" button not working

Howdy.

I'm stuck. When I click on the Next Month button, it simply repositions to the button, but if I right click and open the link in a new tab, I DO get to the next month... (on which neither Next or Previous Month buttons work...)

Reproduced on:
(OS X: Safari, Firefox & Chrome)
(Win 7: Chrome, Firefox & IE 10)

Help? (Please?)

Thanks in advance,

Dan