error (404) (null)

hello everybody

i already installed ejjaberd 7.5 in a win 2000 pro pc, and connected to it 5 exodus client
and worked fine for two days.

but now when i try to chat with anyone user, exodus only show the following error.

error(404) null

and dont't send any message, also if i log on in a pc these one shows me "connected" but in al other pc's my user are "offline" and no one can chat with me because the error above listed.

help! please