Error -25580

Hi All, The following errors are appearing in our message log, without a specific pattern (like seconds or activity level) 09:45:41 (50552) Unable to initiate asyncronous read operation 09:45:41 listener-thread: err = -25580: oserr = 0: errstr = : System error occurred in network function. I'm using an old version (Informix 9.21 TC5) over Win2000. I have attempted to use 'netstat -a -n" and "onstat -g ntt" to try and pinpoint any network issues with the engine, but cannot find any. Has anyone else experienced these errors ? Does anyone have any idea about what system call the messages are referring to? If so can anyone provide information about what to look for to resolve ? Thanks ! Paola