I had run into the same problem, and was searching Google for a solution when I stumbled upon this site. I tried following some of the solutions here, but I suppose they weren't for me (This is not to say, however, that any of these other solutions shouldn't be tried).
I managed to fix this problem in what I guess was a simple but unorthodox way. I figured out that the root of the problem was coming from when C::B makes a folder for the project and its files wherever you want it to. For some reason, the folders which C::B makes are automatically locked, for lack of a better word (this happens on my computer at least). So, I wanted to repeat the actual project-making process and delete the locked file.
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Before I go on any further, I just wanted to clarify this; I was unable to access the project folder form Windows Explorer, nor was I able to change the permissions of the folder when I accessed it via one of C::B's browsing utilities.
*/
Since C::B can apparently open and access the file just fine (and thus can open/delete/rename it), I deleted the file from where I had C::B create it; however, after I sent it to the Recycle Bin, I wanted to check something first before I tried to make a whole new project. Since all I essentially did was just move the folder which contained the project from one place to another, I wanted to see if I could see the folder in Recycle Bin. As it turned out, when I opened Recycle Bin and looked for the folder, there it was; I was able to open it and see it just fine. Intrigued, I restored the folder to see if it retained this state.
To my luck, it did. I was now able to open and edit and do whatever I wanted to the project folder, even from Windows Explorer. I opened the project file in C::B and tried to build it, and it worked! I tried building multiple times with success, and tried changing something and building it again, with success. I thought I would share this with you all to help anyone else who had this problem and also to let the experts on C::B examine this to determine whether or not it was truly a success.
Regardless of whatever, have a good day!