I just recently ran into a problem compiling a C++ project (no, I didnt mean to put this in the C++ forum). I got an error saying that a certain header file couldn't be opened (I had compiled with the same file before). I looked up the error and found that if a .h is read only this error will come up. I then find that the entire directory for the api (its qt btw) is read only (the box is filled, not checked). I remove the read only attribute, but when I check the properties again, its read only once again (UAC is disabled). I have found countless accounts of this on the internet, but none of the fixes worked for me (I tried changing the owner to my own user, disabling UAC, as i mentioned, and using the command line to change the attribute.)
A possibly relevant topic: at around the same time this began happening, I noticed that my hard drive usage went down by around 90GB.... I have no idea why this happened or if its relevant, but any possible explanations for that would be nice too.