TCP/IP issue

Hi, we have a client running v2.6 in a Win2k environment. Every three or four days they are receiving in the server log an Internal Error 3 in Module 1 error. At this point in time they can not connect to the server. The Navision service can be stopped and restarted but they still can not connect - the only way it seems to fix this is to reboot the server. Prior to this they will also receive Internal Error 3 in Module 244, Internal Error 18 in Module 244, and Internal Error 11053 in Module 244 errors. From what I have found on this and other sites these relate to TCP/IP errors and in particular that The TCP/IP connection was unexpectedly closed down at the other end. Now, this client is running the ExpandIT Client Control product which will close a client down after a set period of inactivity. Does anyone think that a client being forced to close down could cause the TCP/IP connection to be “unexpectedly closed down”?? Thanks in advance