Approved messages are not getting to the site?

I am a moderator, and have noticed that messages I am approving are not being posted on the site. for example approved message 18 Aug @ 6.02pm. that was the last message to be approved and showed on the site. Many more after that time were approved, but nothing hit the site until 20 Aug @ 3.39am. Now from 3.39am I have again approved quite a number of messages and they still have not hit the site. I know many other similar groups to mine are experiencing the same problem. Does anyone know what the glitch is, and is there anything I can do to correct it, or is it a yahoo glitch which their techies need to resolve. many Thanks in advance.