numeric problems

I'm using pgAdmin II version 1.3.82 , psqlODBC 7.2.3 ,
postgreSQl 7.2.1. There is a problem when I do an SQL query
with a field of numeric, for eample NUMERIC (10.2). Following
staement causes an error such as "Unable to indentify an
operator '>' for type 'numeric' and 'double precision'..."

select itemNo, listprice from itmt_info
where listprice > 50.99;

And this one works.

select itemNo, listprice from itmt_info
where listprice > '50.99';

It seems all numeric operators are not available on NUMERIC FIELDS. Is there
anyone has done somethings on this problems? Or should I change NUMERIC type
to FLOAT type? Please advise, thank you in advance.

Jack