If you use NFS to mount your root filesystem you should probably faced with this problem:
Root-NFS: Unable to get mountd port number from server, using default
Root-NFS: Server returned error -5 while mounting /my/nfs/server/path/
VFS: Unable to mount root fs via NFS, trying floppy.
The -5 and -13 are the most common on my daily usage, but I [...]