"cannot create TABLE_NAME" error

When I try to create a table and it already exists, I get the error:
"relation 'TABLE_NAME' already exists". However, I tried to create a
table like this:

CREATE table alpx_ (word text not null, field text
not null, expDate date, postingId int4 not null, mall text not
null, sellBuy text not null, datePosted date not null);

and I got the error: "cannot create alpx_"

I was using the 'Pg' module with perl to access the database.  Why would
I get this kind of error?

Thanks, Daniel Stolk