Error getting URL: 999 – Unknown
This error message caused a lot of discussions at both Google and Yahoo! forums (e.g., here, here, and here) and others started to blog about it. Someone provided a workaround using a PHP script but this requires a Web server where this script is running.
Therefore, I discovered another workaround which is http://www.xfruits.com/ that one simply can put in between Yahoo! Pipes and Google Feedburner. That is, just take the output feed of Yahoo! Pipes, use it as input to http://www.xfruits.com/ and burn this output using Google Feedburner and your feeds are back online again ....
PS: http://www.xfruits.com/ offers also other features which look very interesting.
PPS: I'm not affiliated with http://www.xfruits.com/and just found it during my search for a workaround to the 999 error issue.