Corrupted table

In a Perl script I ended up trying to UPDATE a row in my database with a
value that was out of the range. Now whenever I try to do something with
the table I get the error:

    ERROR:  mdopen: couldn't open tablename: No such file or directory

I can't even drop the table, despite the fact that it shows up when I
enter '\dt' in psql. I could probably run destroydb on the
database that contains the table, but I would prefer not too (although if
it comes to it, it wouldn't be too devastating). Is there anyway to fix
this problem.

Note: The type of the field that was out of range is int4. When I
recreate the table I'm planning to make it of type int8, but would like
to know if there is a type for unsigned integers?

Thanks,
Rob Mosher