This is almost certainly a Windows issue, and one that has affected a number of folks. If you do a search for "Read Only Folder Permissions" you will find a number of articles on the cause (being traced back to how Windows does file and folder permissions/security). You will likely have to go into the permissions for the 'C' drive and through the 'properties' take full control of the folders. Then you can change folders from Read Only. There are a number of good articles on the net with the specifics. I had to do this a while back.

Anderton
Try this. Works for me every time. But also check out the discussion here. 

Thanks Craig et al, I will try these suggestions. I'm swamped with other work things but will tackle this when I have a proper moment to do so, and with patience.

I've never had such a weird thing happen with permissions/folder attributes that I wasn't able to quickly solve before. Given that this occurred "out of the blue" without any other updates I can't explain it. Will report back when I have a chance

Windows 7?
 
If so - and this may sound silly but I've had this affect my folder behaviour - check that the services "Application Information" and "Application Experience" are running (I forget which one caused me headaches).

Thanks, but none of these suggestions worked for me.

I see that someone else just encountered this:
http://forum.cakewalk.com...aspx?m=3595881&p=1