Unable to start Deployer because there is another Deployer run

Today I got below error when I was started a new migration from windows plesk 9.5 to Plesk 11.03 and the migration failed

Unable to start Deployer because there is another Deployer run

Solution:
RDP to remote server and delete all files in below folders

C:\Program Files (x86)\Parallels\Plesk\PMM\msessions
C:\Program Files (x86)\Parallels\Plesk\PMM\rsessions
C:\Program Files (x86)\Parallels\Plesk\PMM\tasks

After that restart the plesk migration agent.

If the issue still persists then restart the server once and try again.