Such problem areas are found to some extent in many terrain mesh addons.  Not necessarily the authors fault, but rather caused by the differences in data accuracy used by: MS (less) and the author (more).

No need to reinstall, as terrain mesh's add-ons do not write over the default FS files.  They are separate files that are called in place of the default files.

If you wish to stop using the new mesh, simply uncheck its box in the Scenery Library-Settings window. You must restart FS9 for the change to take effect. If you wish to delete the files, be sure to delete the area from the Scenery Library-Settings window before removing the files.

You might contact the author to see if he/she has issued corrected files, or maybe try another mesh covering the same area. Saw one for that area here in the FS9/Scenery/page 16, sounds like the same area but is LOD9, dont know if thats the one you have. There is also the 70m Global Terrain mesh on the main download page.

You might also post your problem in the Scenery Design forum as those are the experts at making and fixing scenery. Beyond my scope of knowledge..

Cheers,
Dave  

Payware is likely a better choice.  Entire USA for $35 . Landclass separate payware or both for about $40.  I did the separate payware. No problem with floating airports etc.