Can't write lock file

Here are the results of

df /tmp/
Filesystem           1k-blocks      Used Available Use% Mounted on
/dev/hdc6               253840    243504         0 100% /

df -i /tmp/
Filesystem            Inodes   IUsed   IFree IUse% Mounted on
/dev/hdc6              65792   24415   41377   38% /

The above information seems to me contradictory in that df /tmp reports
that 100% of my 1k-blocks are used, while df -i /tmp/ reports that only
38% of inodes are used. I don't know what to make of this. Nor am I sure
if this is why I can't use postgres. Nor why this problem has occured in
the first place.

Totally in the dark,

Mark