Try Optimizing the Database:
- For most recent versions of ACDSee, click Tools | Database | Optimize Database. For previous versions of ACDSee, click Database | Optimize Database.
- Click Next.
- Put a check in both boxes then click Next again twice.
- Click Finish.
If the above did not resolve the issue you can use Windows Explorer to delete .cdx files of the ACDSee database. The exact name and default location of the database folder depends on the Operating System and version of ACDSee you are using. For information regarding the default database folder name and location by version, click here. For more information on how to delete the cdx files please refer to this Solution Article.
Please ensure to only delete the .cdx files as the other files are for the database information that you have assigned to the images.
If deleting the .cdx files did not resolve the issue, please delete the Thumb1.fpt and Thumb2.fpt (not all the fpt files) in the same folder and test if the issue has been resolved.