Hi

One metalink note describe ORA-01115 as

The main causes for an ORA-01115 are:

1. HARDWARE PROBLEMS

- Disk controller problems: the most common, and usually intermittent.

- Disk problems: these include bad blocks, disk malfunctioning, etc.

2. DATA BLOCK CORRUPTION (AT THE PHYSICAL LEVEL)

Usually caused by previous hardware problems.

3. PROBLEMS HANDLING VERY LARGE DATAFILES

In the same note it suggests to check the objects involved.
"If the datafile belongs to a user or index tablespace, you may also
address the problem as an object recreation issue if the ORA-01115
occurs consistently against the same objects (tables, indexes, etc.).
The following query returns the object in which the bad block is: "

SELECT SEGMENT_NAME, SEGMENT_TYPE FROM DBA_EXTENTS
WHERE FILE_ID = 4 and 8713 BETWEEN BLOCK_ID
AND BLOCK_ID + BLOCKS - 1;

SELECT SEGMENT_NAME, SEGMENT_TYPE FROM DBA_EXTENTS
WHERE FILE_ID = 20 and 154540 BETWEEN BLOCK_ID
AND BLOCK_ID + BLOCKS - 1;

It will be a good idea to check your alertlog and relevant trace files for more information.

Out of curiousity, are you running any backup job at the same time??

Rgds
Adnan