Issue with receiving /whispers immediately after logging to the realm

Hello,

When I log to Icecrown server and immediately start typing in Global , LFG or Trade chat channel I sometimes receive very few whispers from other players. Then, after few minutes, I suddenly receive all those whispers from many different players which I did not receive. As if they are stuck and then released at once. There is obiously delay from the time these players send me message and by the time i get it, however, I don't know why. Does anyone have similar problem and could you give me solution?

Thank you.