Maybe these articles can help: How to unlock is listed. 
& This file is currently locked by another user error opening or saving clients. 

Nope. Not locked by another user or locked on purpose. What is "UninstallInfo"

Make sure you and your staff are completely signed off of ProSeries and the network, follow the directions in the second article above. If the error continues perhaps restore a previous version of the program. Let me know if this was resolved for you or if you're still having this error pop-up.