UniBeast: Couldn't remove installation packages

I cannot install UniBeast to USB. This is all I get from UniBeast.log. Please help debug it

10/04/15 13:02:13 - Starting UniBeast 6.0.0-20150930
10/04/15 13:02:34 - Mounting Volumes...
10/04/15 13:02:36 - Copying Files...
10/04/15 13:05:37 - Couldn't remove installation packages