Mouse not Working

Help! My mouse has lost all functionality in WordPress.com. I am using a Macintosh – and the result is the same whether I’m on my laptop or computer. When editing content on a page, as soon as I try to select any text, the mouse stops working. I can’t do anything except arrow up/down. I CAN however, use the mouse to edit and select in the HTML view. Please help, this is so frustrating. I’m new and don’t really know what to do! I have tried firefox and safari – both with the same result.