SHARING FILE ACCESS PROBLEM

dear member,
MY self dharmendra, i have a problem from last week. Problem is that i have installed a window 2003 enterprise server in hp ml100 server. i have shared drive “d” and all the client computer(around 20) access that shared folder and working directly on that folder. my problem is that just before one week, all employees told me that when they are working in server, it is hang sometime for a few second(i think 3 or 4 second). For this problem i have check all lan cable, all lan switch, scan all computer include server. But i didn’t get any solution.
it is very urgent pls provide me solution….
my email id is :- idsindia@ids-inc.net