Mohammed,

Are you by any chance using Smart Posting?  If yes, turn it off!

I am Not using smart posting.  

I would recommend that you stop/start the Actian (Pervasive) Database engine on the system that host the data and reboot the workstations afterwards... If this is a standalone computer, then you can just stop/start Actian (Pervasive) on the standalone computer. Here is a link from our client knowledgebase that may assist you with your error: Error: "Another Sage 50 user or workstation is accessing this company area or performing a similar company process" and user sessions are not closed out properly

Are you using the latest version of Sage 50, or have there been recent updates Wesley Financial Group that might have caused compatibility issues?