Stored procedures and relations

Hi everybody,
I have a stored procedure that drops table A and then creates table A
again. The table A has no constraints on any columns. When I execute
the stored procedure by saying: SELECT sp_myproc(); It gives me an
error saying : Relation 68428 does not exist.

When I remove the CREATE FUNCTION and the stuff used to make it a
stored procedure, and run the commands in the procedure, it works
correctly.

This behaviour is observed on all stored procedures on PG-SQL. I would
really appreciate any help or interpretation of this error. By the
way, the same stored procedure (with the syntax changed of course)
works perfectly on MS SQL Server.

Thanks in advance.

Regards.