I didn't expect there'd be anyone there but I got straight through to a specialist who was very helpful. They helped me find out what was up and how to fix it. Just wanted to say I think this is a great feature and please keep it running.
For those interested, here's more detail on this subject from the AdWords Help Center:
Ask a specialist via Chat
[adwords.google.com...]
What the heck, I may as well also quote the content on that page, as it's a quick read:
Google Live Support allows you to receive immediate response to your questions via a free online chat session with a Google AdWords representative.The Ask a specialist via chat button will appear on AdWords Help Center pages when an AdWords Specialist is available. You may not see the button all of the time, but it will be displayed as soon as a specialist is free.
If you'd like to get help from a chat Specialist, try visiting the Contact Us page and selecting the appropriate category. If we're available, simply click the button labeled Get live help from an AdWords Specialist to initiate a chat (no special software required). If you don't see the button, we're not available to chat at that time. However, we're always available via email, so please feel free to send us your questions using the form provided. We'll be happy to answer your questions.