In the last few days, my iCal has been giving me the following error message when trying to access my Yahoo! Calendar via CalDAV:
The request for account "Yahoo! Calendar" failed.
The server responded with
"502"
to operation
CalDAVAccountRefreshQueueableOperation.
Yahoo! have acknowledged this is a problem on their side:
We are aware of a Calendar (Proxy error) and our engineering team is working to resolve this issue. We apologize for the inconvenience and hope to have it resolved soon.
(source: Syncing / Mobile Sync | Yahoo! Calendar Help)
update 2nd November 2011: I am no longer seeing this error message, and Yahoo! have removed the notice from their help page. Looks like the issue has been resolved!
update 3rd November 2011: Seems like I spoke too soon, the error is back!