IDS 7.3 TC3: Unable to initiate asyncronous read operation

Hi, we're using IDS 7.30 TC3 now on NT 4 SP3. Sometimes every day, sometimes every two or three days, the following error message encountered : (N) Unable to initiate asyncronous read operation, where N=7, 723, 724, 726 etc. The message usually accompanied with the next one: LIstener- thread err=25580, oserr =xx, string := System error occurred in network function, where xx=0 or 35. ONCONFIG parameteres: NUMCPUVPS=2 to 6 NUMAIOVPS=1 NETTYPE=onsoctcp,1,,NET Number of concurrent sessions <50 Number of CPUs =2 Right after the error, the new connections establishment time: up to 7-10 min. Any ideas or help will be appreciated. I.Olexenko