"Access is denied" for LocalService and NetworkService accounts??

Hello,

Two days ago I've noticed that some of my system services aren't
starting
and returnig "Access is denied" error. Problem concerns to services
that
are logging to NetworkService and LocalService account only. My idea
was
to change logon account to LocalSystem and now everything works fine,
but
I don't want to leave it for that manner for a long time. As we all
know
LocalSystem account have all privileges and therefore is very unsafe.
Maybe you had such error in the past and can help me to solve it?? I
have
no idea how to enable locked accounts..

br