Sometimes when trying to open the Cell Library dialog box:Or after clicking the ‘Browse Cell’ box in the Place Active Cell dialog: In both cases the Cell Library does not load.
To solve this issue please follow the steps below:
1. Using Windows File Explorer navigate to C:\Users\username\AppData\Local\Bentley\OpenBuildingsDesigner\
2. Delete or rename the folder "10.0.0"
Also see: Regenerating preference files to help resolve random odd behavior