IMDb is currently changing to a new, quicker update system. However, the Update version of the database is still maintained by the older system, which requires an overnight system rebuild This means that changes that show up on the display pages will not be available for update for 24 - 48 hours.
If your changes have just shown up, you should be able to submit corrections in a day or so.
If this is not the problem you are having, please post a reply with more detail.