This may be a permissions folder, but it also depends upon where you are trying to write to, and especially if you upgraded / clean installed Windows 7 while carrying over folders from a previous operating system.
If you try to write to System Protected areas, like %systemroot% (aka \Windows\System32\) or %ProgramFiles% (aka \Program Files\) you'll get an error - this is by design.
If you are trying to write to a folder you definitely have access to write in (My Documents, etc) then check to see if the file is read only.
If you are trying to write to a folder that you created using an older operating system after having clean installed Windows 7, it can definitely be a permission issue. The easiest thing to do is to go folder by folder and take ownership of the folders that belong to you (meaning leave out \Recycler, and the hidden \System Restore folders, and other similar system created folders if they exist), but this can be a daunting task, as you'll then need to also add yourself to the permission list to allow yourself to read, write, etc. to those folders.
There is an easier way to fix it depending upon your scenario from the three I have listed, so please post back on which scenario fits you....