I noticed that the b2evolution ping feature has been failing for blo.gs for some time, looks like some other folk have encountered the same problem. I looked up the blo.gs ping documentation and discovered they've recently unified the ping service with the one at Yahoo! (who bought them out a while back), which means the RPC address has changed.

It seems easy enough to fix, open up the file inc/_misc/_ping.funcs.php and look for this line:

$client = new xmlrpc_client('/', 'ping.blo.gs', 80);

Change it to:

$client = new xmlrpc_client("/RPC2", "ping.feeds.yahoo.com", 80);

And it should start working again. (At least I hope so, I'm just about to try it...)