Hadn't heard of this problem before, but it does seem fairly common.
It sounds like it's a permissions problem. You have to explicitly tell Windows to propagate permission changes to subfolders, so just changing them at the top level may not fix the issue.
Here's a site that lists clear instructions on how to reset permissions manually.
Here's a program that sounds like it will do the same thing.
Big disclaimer - I can't vouch for either of these methods personally, as I haven't experienced this issue.
What I do like about the manual method is it will only affect the files/folders in your user directory - I wouldn't want to change permissions on all directories. I'm not sure which files/folders the program will affect.
Good luck!