Intermittent problem unable to access to server's folder

Hi,

One of my user's PC is running on Windows98 Operating System is having
problem with his network.
This machine is able to login to the network and access to the file servers.
However, there is intermittent problem that this machine is unable to access
to one of the server. It will prompt the error message stating "\\Servername
is not accessible. No permission to access resource." However, all users are
granted with read access to this server. On the other hand, the user is able
to access to another server folder.

I have also checked on the server, and the folder is granted with read and
write access to everyone. After several times rebooting the PC, the user is
able to access to \\Servername. This really puzzled me on what is the actual
root cause of the problem. Can someone help to advise on this matter?

Thanks a million in advance.