Issues with Yahoo! Mail beta and features

Sometime back Yahoo introduced the mail client like look and feel in beta phase and I believe it was much appreciated by all and welcomed. Though there were some issues with the mail access (specifically if I am behind corporate firewall) with the page just freezing at the "Loading" screen, it still was a good deal and most of the issues have been sorted out.

Recently, Yahoo introduced another functionality to integrate Yahoo! Messenger inside Yahoo mail in the browser as a direct response to Google's integration of Gmail and Google Talk. I really liked that part as that gave me the freedom to not to download the sometimes intrusive Yahoo! Messenger. I was really enjoying using the two together till today the problem shown on the screenshot above appeared. I am not sure it is related to the same feature addition, but it sure does look like it. I believe the problem was existing for at least 2 hours though now it is solved and I am able to get into and read my mail.

While I understand that any addition of new features will cause something to break, what I don't understand is how can a company like Yahoo! allow such incidents to occur in production? Isn't there enough testing and QA done?

I don't know.