NFS exports no longer work?

[Dean]

I did the dist upgrade thingy (as described in the wiki) on my server, and  
now all my clients can't access the nfs share that I had exported. I tried  
rebooting the server and the clients, but I get the same error no matter  
what. I don't have the server firewalled or anything... The error is as  
follows:

dean at dim:~ $ mount /mnt/net/
mount: RPC: Remote system error - Connection refused

I don't know what to do! I haven't changed any settings on the server,  
just upgraded.

Thanks,

Dean