Sometimes Google outsmarts itself - in this case I'm talking about something as basic as phone extensions.  In my old contact/phone system I would have the extension within the phone field and the phone would only dial the first ten digits - leaving me to dialing the extension - but the extension was visible.  The Google G1 on T-Mobile converts the letters Ext over to their numeric value - such as 398 - and tries to dial the whole phone number including 398 and the extension.  This is great if you enter a phone number of 800-getfood to call your food supplier, but it's not so good for dialing an extension.  The correct answer to solve the riddle is the use of a comma.  A comma after the number is a pause - the phone will then dial the number and then the appropriate extension for you after the automated attendant answers.  The bad news to this is that if the phone is answered by a human (keep dreaming), they'll get a bleep bleep earful.