A call to PageAddItem(), made within _bt_pgaddtup(), is where this failure seems to ultimately originate from. What we're missing here is the reason for PageAddItem() returning InvalidOffsetNumber. That is usually, though not necessarily, separately available within a WARNING log message, which you haven't included here. Could you please let us know if there is a WARNING that you didn't include just prior to the ERROR?
No warning I'm afraid. These are the statements I see on the Postgres log file:
2012-10-01 13:09:12 WEST ERROR: failed to add old item to the right sibling while splitting block 191 of index "crc323"
2012-10-01 13:09:12 WEST STATEMENT: INSERT INTO test (projectid,crc32,name,path,command,details,output)
