What's it? "LockRelease:"

Hi All!
Sorry for my english.
I use 6.5.2 and C interface.
When program has been run i've recieved the message:
NOTICE: LockRelease: locktable lookup failed, no lock

/*The part of code:*/
PQexec(conn,"declare grh1 cursor for select x1 from test where x1='RRR'");
res10=PQexec(conn,"fetch all in grh1");
PQexec(conn,"close grh1");
/*end_of_part*/

The program runs well without this part.

Thanks in advance

Vitaliy