For some reason this is a pretty commonly reported issue after running a Track-It! update. If you follow the steps in this article to completely rebuild the search index files on the Track-It! server you should be all set. Keep in mind that it could take several hours to fully rebuild the search indexes:
While it is rebuilding the index files you will see a "CurrentlyFullIndexing" file in the SearchData folder mentioned in the article. If you periodically refresh the SearchData folder you should see that the files are growing in size. Once the "CurrentlyFullIndexing" file goes away, you should be all set.
Really strange. We've gone from 11.1, 11.2, 11.3 all without having any weird glitches like this. Software... amiright?