Application related
If it is the same file name repeatedly getting the cannot read error for multiple users, then it is likely to be application-related, and you will need to rebuild those files.
Network related
If it is network-related, it is likely to affect many different files in the HSoft\Data folder, and it will be intermittent and may affect one or many client workstations on the network.
To confirm that it is network-related, ask the affected user to work on the server for a period and establish whether they have any "cannot read" errors whilst working on the server. If they do not, it is almost certainly network-related.
If it is network-related, we recommend asking your IT consultant or network engineers to investigate why packets are being dropped on the network.
Quite often this is related to:
DNS Issues
Antivirus
Firewalls
Incorrectly mapped drives
Faulty hardware