File access problems

I am finding that when I attempt to move files from
the "desktop" to the "My Documents" directory structure
or even within and around the My Documents directory
structure, I end up with an "Access is denied" message
when I attempt to read the file. I am not able to
delete, rename or view these files once they have been
moved. My recourse to date has been to enter safe mode
where I am able to change ownership permissions and then
regain access to the files. Why is this happening? Why
can't I correct this without going into safe mode?
Better yet, how can I prevent it from happening in the
first place?