Database location - Each installation should be accessing the same exact Database. If you are using drive letters, please confirm that the drive letters are mapped to the same shared folder.
File Permissions - The Windows user logged into the workstation needs full access (read, write, etc) to the database file and folder in which it resides. Giving explicit access to the actual users can circumvent any possible problem with file permissions. You can test this by temporarily renaming the .hdf database file and by creating a text file in the database folder.
Sometimes anti-virus and security software can interfere. Try disabling all security software temporarily and see if that helps.
Installation version - Each installation accessing the same database should be running the same version of the software.
Backup folder configuration - The backup configuration is configured separately on each installation. Either turn off the backup or verify that the location of the backup is valid, i.e, plenty of space and appropriate file permissions.
Test network performance
Verify dates and times on all computers involved are correct. Less than 2 minutes difference isn't relevant.
Mini-dump - If the program crashes, it attempts to create a dump file in the folder c:\HicProMiniDump. This file can then potentially be analyzed by the developer at Holladay Software to determine what is the problem. If that file can't be created and the program attempts to create a dump file, you could get an error message stating that the dump file couldn't be created. Obviously for the file to be created, the appropriate file permissions are required.