I cant access to my sharedocs Please help

Hello,
i have a problem using my sharedocuments , before , i share all the document in the cyber cafe i work on, i use to acces all the files from all the computers, using my server , but now , there some computers on my share docs that i can't access, it tells me : not accessible because u might not have permission to use this network resources, contact the administrator of this server to find if u have access permission .The network path was not found.

i receive this message to 3 of the computers which are on my network, yet am the administrator, Please i need your help