Database Software

I've had a database that's been humming along with an Oracle Text index for about a month now, doing daily synchronizes to keep it up to date. One day, it began giving me the following error, and has done so ever since:

ERROR at line 1:
ORA-20000: Oracle Text error:
DRG-50857: oracle error in drekmap (lob write)
ORA-00600: internal error code, arguments: [9999], [], [], [], [], [], [], []
ORA-06512: at "CTXSYS.DRUE", line 160
ORA-06512: at "CTXSYS.CTX_DDL", line 539
ORA-06512: at line 1

The command I'm running in SQLPlus is:
exec ctx_ddl.sync_index ('us_ws_ctx_idx1', '256M');

I tried varying the memory and the parrellelism parameters, to no effect.

I tried synchronizing with the following to produce an output log:
exec ctx_output.start_log ('contextbuginfo.txt', false);
exec ctx_output.add_event (CTX_OUTPUT.EVENT_INDEX_PRINT_ROWID);
exec ctx_ddl.sync_index ('us_ws_ctx_idx1', '256M');

The output log didn't appear to have anything particularily interesting or obvious. Here is the tail end of it:
---
10-35-00 09/22/06 Errors reading documents: 0
10-35-00 09/22/06 Index data for 3155931 documents to be written to database
10-35-00 09/22/06 memory use: 268435504
10-35-00 09/22/06 Begin sorting the inverted list.
10-35-02 09/22/06 End sorting the inverted list.
10-35-02 09/22/06 Writing index data ($I) to database.
11-18-34 09/22/06 Wrote 776605 rows (28611 big rows) to $I.
11-18-34 09/22/06 Writing index data ($K) to database.
11-19-46 09/22/06 Wrote 3155931 rows to $K.
11-19-46 09/22/06 Writing index data ($R) to database.
---


Does anyone have any ideas on how to fix this problem?