It is not really the number of rows or columns, but these can be contributing factors, that effect performance but it can be a number of things.
Can you generate the sql script for the table definition by right clicking on the table in enterprise manager and going to all tasks --> generate sql scripts?
Can you also post the sql for the query?
Also let us know about constraints, triggers and indices that may be on the table.
If one brings so much courage to this world the world has to kill them or break them, so of course it kills them. The world breaks every one and afterward many are strong at the broken places. But those that will not break it kills. It kills the very good and the very gentle and the very brave impartially. If you are none of these you can be sure it will kill you too but there will be no special hurry. Earnest Hemingway, A Farewell To Arms.