Because Lightroom 4 has different Basic Panel controls than Lightroom 3, if you have created presets in Lightroom 3 that use Basic panel controls, you may  be finding that they don’t look as expected now that you are using them in Lightroom 4.  Sharad Mangalick, one of the Adobe product managers for Lightroom, has written a post on how to update your presets for Lightroom 4, over on the Lightroom Journal.

By the way, this is an excellent blog to follow to keep up on Lightroom bug fixes, new releases, and more.