Message may have not been sent because a timeout occurred:

Thanks for taking the time to report this bug and to improve Ubuntu. Are you experiencing high network latency? Are messages actually not getting sent or are you merely getting the warning? Are you having any other trouble using Internet- or network-based applications, such as Web browsers, mail clients, P2P apps, and so forth?

messages actually are not getting sent.

Are you experiencing high network latency? Are you having any other trouble using Internet- or network-based applications, such as Web browsers, mail clients, P2P apps, and so forth?

yes i do, sometimes Internet get slow, and i can say that it is due to ubuntu, because i have other pcs in the network with ms windows and they are ok

for example yesterdey, my internet connection was shut, as i said it was not due to my internet provider, but to linux, my sister has ms windows 7 and she was surfing

thank you for your bug report, the issue should be sent to the software writters on pidgin.im by somebody having the bug

Here is an upstream ticket. I think it is the same issue:

"MSN timeout/ connection errors mid-conversation"
http://developer.pidgin.im/ticket/3330