Before we can work further, I'd like to gauge if the issue can be replicated by other users or other computers first. That said, worth a look into.
The visual editor is nice and all, but for now you might need to use the "Standard Editor". The setting to change this is found here under "Message Editor Interface". I can't imagine why the Preview button would crash the browser, though.
As standard practice, also make sure your browser's up to date - check Microsoft Update and make sure your copy of IE has the latest security patches (or upgrade to Internet Explorer 10).