Be sure to check the guidelines/rules for this contest, and be sure you are okay with them before submitting. This is one of the contests that wants all rights, royalty-free, forever.
From ING's rules:
"Each Grand Prize winner grants ING DIRECT a perpetual, irrevocable, fully-paid, royalty-free, transferable, non-exclusive, world-wide right and license in and to his/her Story, with rights to sublicense, to use, copy, modify, reproduce, market, publish, distribute, sell and otherwise exploit for any purpose whatsoever, including without limitation, modifying the Story, copying the Story, improving the Story, making derivative works thereto, reproducing the Story and selling or otherwise distributing the Story."
A similar contest that had stipulations like this was the Woman's Day contest (I think it was last year?).