Slow access on shared folders on linux

I have linux mandrake 8.0 as the server in a 10 pc network thare are no problems accessing the servers shared folders, When you open network neigbourhood you are shown the list of computers, you open the server and the default shared directory's come up straight away any folders that you open inside the shared folder can take up to 30 seconds to open so if you are in word saving a document on the server it appears that word has locked up but is just accessing the server. all pc's are using 100 Mbps network cards there is a 19 port switch beside the server and everything is operating at 100 Mbps