Little bit of a brain lock here since it has been two years since I used classic.
But if you followed the directions for moving you would not have updated the control panel settings when importing the posts.
Besides the rebuild section I seem to recall there was more settings for the search feature for how and what to index. In the primary settings. You may find you will still need to reindex after you change the search settings.
There are sticky topics in this forum " UBB.classic Version 6 Assistance" with links to all the old documents.
