Email Macro won't Send to Distribution List

I've been working on a macro that sends out an email when a button is clicked which is pretty simple. The issue I'm having though is that it will not recognise a Distribution list entered in the recipient line. I've been using Ron de Bruin's site extensively but even using his guide for adding a Dist. List hasn't been successful.
I'm running it on Excel 2007 through Outlook 2007 on Vista.

Any help/suggestions to make outlook identify the correct Dist. List would be greatly appreciated!

Thanks

Dan