Pg dump Error

I have a problem with pg_dump on 2 computers. On the first computer, pg_dump
runs very well, but on the second pg_dump has a error :
pg_dump: reading triggers for table "ph57"
pg_dump: reading triggers for table "phts"
pg_dump: reading dependency data
pg_dump: SQL command failed
pg_dump: Error message from server: message contents do not agree with
length in message type "D"
message contents do not agree with length in message type "c"
server sent data ("D" message) without prior row description ("T" message)
pg_dump: The command was: SELECT classid, objid, refclassid, refobjid,
deptype FROM pg_depend WHERE deptype != 'p' ORDER BY 1,2
pg_dump: *** aborted because of error

Please help me. Thank you very much.
Sorry for my English
TuanHa