Na tom linku k icqhelp to našlo toto :

Error number: 0301, 0302, 0303, 0304, 0305, 0306, 0307, 0314, 0700, 0701, 0702, 0703, 0714, 1503.
Error message text: Failed to send the message. Please try again later.

These messages indicate that ICQ has temporarily disconnected from the ICQ network or has lost the connection with the recipient's computer, and therefore is unable send your message.

In order to properly reconnect to ICQ, please shut down ICQ and restart it.
To shut down ICQ click the Main menu -> Shut Down.
In order to restart ICQ please click Start->Programs->ICQ 5->ICQ 5.1