WLM not reliable at sending all messages

WLM occasionally does not send my messages to the recipient or send me the messages from the recipient.

This problem is without error, which is worse, it would be good to know that my message has not been delivered so i can re-send but instead the recipient and i just sit there and wait for a reply which gets really annoying and wastes lots of time.

Anyone have any suggestions? Both my sister (@hotmail) and myself (@gmail) running on the WLM network have this reliability issue with various contacts but more often with some certain contacts.

My sister and I are both running Toshiba laptops using wi-fi to the same router and modem.

Thanks for your time