Block Corrutiop in alert log but RMAN validate found no curruption

Hi All,

We have  10.2.0.5.0 and 9.2.0.8.0 database on AIX reporting in alert log

Corrupt block relative dba: 0x14d3a7df (file 83, block 1288159)

Fractured block found during buffer read

Data in bad block:

type: 6 format: 2 rdba: 0x14d3a7df

last change scn: 0x0006.428011a7 seq: 0x1 flg: 0x06

spare1: 0x0 spare2: 0x0 spare3: 0x0

consistency value in tail: 0x696c652d

check value in block header: 0x5ad

computed block checksum: 0x6449

check value in block header: 0x5ad

computed block checksum: 0x6449

Reread of rdba: 0x14d3a7df (file 83, block 1288159) found same corrupted data

so we ran export of the object and "backup validate check logical datafile 83;" and select * from V$DATABASE_BLOCK_CORRUPTION ; - this found no corrupt block.