Try restarting your computer.
If that does not work then There are a few possibilities.
1. The front end file TATEMS file is corrupted you will need to apply the current update Close TATEMS and then if you don't have the current update on your computer you need to re-download and open the current update. http://tatems.com/updates then re-link to the data file on the server. or
2. Your permissions to the folder where the data file is stored have suddenly been lost and you don't have full read write access to the folder on the server anymore. you can test this by having everyone close out of TATEMS and then see if you can from your computer, logged is as the current user, rename the folder on the server where tatems2005be.mdb is stored.
or
3. Your permissions to the folder where the front end file is stored on YOUR computer C:\Program Files\TATEMS 2005\ have suddenly been lost and you don't have full read write access to the folder. You can test this by closing TATEMS and see if you can rename the folder TATEMS 2005 that is in C:\Program Files\ If none of those work then it could be the data file is corrupted or you have some other networking or permissions issue.
Or
I could be that you just need to do a repair of the Microsoft Access 2002 runtime in Add-Remove Programs in the Windows Control Panel.
We can also take a look remotely if all else fails.