Error in Domino

I have 6 domino servers in 4 location.
All this servers use Domino R5.07 and running on windows NT 4 with SP5.
One of these server got an error in domino console :
“Error on listening function : The TCPI/IP Protocol Stack reported that it run outof memory.” then follow by this error : “Insufficient TCP sockets are available. Consult your vendor’s TCP/IP documentation to increase the maximum number of sockets.”

Server can not shut down, and have to power off, then boot to NT system. It take long time in blue NT screen, then server will restart again.

I have got two times this problem. After I reinstalled windows, server will running normally.

Can anyone help me !
Is this NT problem or domino Problem ?

Thanks