What does it mean?
"Dictionary Invalidated" is generated by the Biblioscape indexing engine. This error message usually happens after deleting records, adding or editing a record. The message suggests that the words table for an indexed search is no longer valid, and needs to be rebuilt.
What do you need to do?
If you still can access menu commands, click the menu command "File | Database | Update Search Index". Biblioscape should start to rebuild the search index. A small window should be shown with a progress bar. If this does not happen and other error messages are generated, you need to kill Biblioscape, then delete all files under "C:\Program Files\Biblioscape 4\Index\" directory. When you start Biblioscape again, those search index files will be regenerated.
Note: This error message is related to the old full text indexing engine. In Biblioscape, if you go to "Tools | Options" window, on the "Database" tab, "Full Text Indexing" section, check the box "Full text live indexing". If this box is not checked, Biblioscape will not use the old full text indexing. The old full text indexing engine doesn't work reliably on some system. If you want to use it, be sure to get the latest critical upgrades for version 6 at http://www.biblioscape.com/patch_readme.htm, for version 5 at http://www.biblioscape.com/patch_readme_5.htm. For version 7, all the releases after version 7.17 includes the critical upgrade already.