I have a few ideas. You didn’t give much information as to the client machines or your environment. But if the drive that the shared folder is on is corrupted this could cause freezes to the clients accessing the drive. Does the freezing happen on the server as well?
Can you check disk manager and let me know the status of the drive in question?
Another possible issue could be a virus or mal-ware file on that drive. What anti virus software do you have installed?
Is it configured to lock out network activity for a period of time if it encounters an infected file like my Macafee 8.5i does?
Can you run a full scan of the drive in question or check your anti virus log files?
What does the event viewer on the system in question say? How about on the client?
With answers to all these questions your problem should be solved or at least put you on the right track for fixing it. Please post the answers to the questions and any other information you have regarding the issue.