Disk problem has stopped 'df' from working

[support-lists at petdoctors.co.uk (Nigel kendrick)]

Hi folks, probably not CentOS specific but any help appreciated:

One of our CentOS4 servers crashed and when checked there was a disk problem
which turned out to be a faulty SATA cable on one of the RAID 1 drives. This
was sorted and the server brought back up after the usual disk checks and
all has been well for the last week. Today, however, I tried 'df -h' and
got:

Filesystem            Size  Used Avail Use% Mounted on
df: `': No such file or directory

I can't recall whether I tried the command just after the server was
restarted (ie: whether this is a new problem) but any pointers towards
possible causes/fixes would be appreciated.

Thanks