index_param failed

Dear list,

from the log I am getting these errors like

====================== <= bdb_equality_candidates: (uid) index_param failed (18) <= bdb_equality_candidates: (uid) index_param failed (18) <= bdb_equality_candidates: (uidNumber) index_param failed (18) <= bdb_equality_candidates: (memberUid) index_param failed (18) <= bdb_equality_candidates: (uid) index_param failed (18) <= bdb_equality_candidates: (uid) index_param failed (18) <= bdb_equality_candidates: (uid) index_param failed (18) ==================================

could any one tell me the possible reason behind it and how to fix it ? thanks