mount.nfs:connection timed out

[Linda]

I'am looking for suggestions to solve a nfs problem. I did the updates 
of 8.04.3 LTS  that required a reboot this week. I have several 
directories that are shared via nfs. After I rebooted the machines one 
of the nfs directories would not mount on the client. The directory is 
for an external usb hard drive used for backups. I tried unmounting the 
directory and remounting it on the server than doing a exportfs -rav It 
shows it exports the directory to the right ip address. However the 
client continues to give me the error mount.nfs.connection:connection 
timed out. I am at a loss to why this one directory will not mount on 
the client when all the other nfs directories are working fine. The usb 
drive is properly mounted on the server. Any ideas on what could be 
going on?
          Thanks
            Linda