Delete failing on table with spatial column

I'm trying to delete ~670M rows from a table with a spatial column in Oracle 11.2.0.3 running on solaris.  But, I keep getting the following:

The command:  delete from srqv.last4 where datetime between sysdate-5 and sysdate-4;

ERROR at line 1

ORA-13236: internal error in R-tree processing: [MDRCNCCMTTXNg]

ORA-13249: mdrcncupdidx:16

ORA-13236: internal error in R-tree processing: [reading node (mdrbdlrt)]

ORA-29400: data cartridge error

Error - OCI_NODATA

ORA-06512: at "MDSYS.SDO_IDX", line 12

ORA-06512: at line 1

ORA-06512: at line 11

This happens even when I try to delete only a few records at a time, so it isn't a size error.

Any suggestions?