A huge thank you to all who helped me solve my problem. To synopsize for those keeping a lessons learned:
The sequence table got out of sync with the with the column being sequenced. This was mot probably caused by reloading data improperly without regard for the sequence generated value.
The sequence can be resynced using the command:
select (setval('my_seq',max(my_col)) from my_table;
or in my case the actual command which solved the problem:
SELECT setval('datadef_datadefindex_seq',MAX(datadefindex)) from datadef;
later,
ben