need solution for cachelookupfailed error

Hello,

I have installed PosgreSQL 7 on Red Hat Linux 6.1. I am developing a CRM system using front hand "Enhydra" and back
handas "PostgreSql". I have encountered the problem in 
developing a function. The error message I receive is fmgr_info: function 18816: cache lookup failed. The structure of
tableand proceedure I use is as follows. 

Company Table Structure

create table company ( id serial PRIMARY KEY, comp_name varchar(100), shortname varchar(20));

Insert Function for company table

create function insertcompany(varchar(100),varchar(20)) returns int4 as
'begin
     Insert into company (comp_name,shortname) values ($1,$2);
     return 0;
end;' language 'plpgsql';

Now If I run the above function from the psql command prompt with the following syntax
   select insertcompany('iengineering.com','eslab');

Then It gives me the error message fmgr_info: function 18816: cache lookup failed.

If I Insert the values into the company table from the psql command prompt without using the function with the
followingsyntax 

   Insert into company ( comp_name,shortname) values ('iengineering.com','eslab');

Then It inserts the value with out any error and I receive the message INSERT 97424 1 on the command prompt.

One row value get's inserted. But I can not insert values using the function call.

If you have any solution for the error message fmgr_info: function 18816: cache lookup failed. Then suggest me the
solutionfor the above. 

Thank You
Kiran Patel