Hi,

I assume you are creating the new web site in the Site Manager interface.

Have you tried to restart the application?
Also, you can try to kill the w3wp.exe process (low level restart option :-)) - it seems that the file was locked but not unlocked - this may do the trick (or also rebooting the computer where the CMS is running, unless it is a production web server).

Also, please check the disk write permissions set for your web project folder.

Best regards,
Juraj Ondrus