Error Using CLUSTER

I started using CLUSTER a few weeks ago and it worked
(no errors) and the performance of the database
improved. However, When I ran CLUSTER again, I got the
following error:

ERROR: cannot create pg_temp_2558977013: File exists

Here is more information that may or may not be
relevant:

1. I am running PostgreSQL 7.3.1.
2. The table has a little more than 16 million records
3. I am pretty sure I am not running out of disk
space: The size of the partition is 126 gigabytes and
only 28 gigabytes are used.
4. The table has 5 columns: (int, date, date, float
date)
5. There is one index on the table: (int, date, date).

Is my database corrupt? Will CLUSTER corrupt my tables
if it doesn't finish successfully?

Thanks.

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