Linux memory leak?

[Alan Scheinine]

  > Sometimes (e.g. after 14 days of
normal operation) our nodes report unusually high memory usage even
without any user processes active.

 Do you have a problem with paging to swap space?  My experience
with Red Hat 6.2 is that memory fills up with everything I have
used, such as files that have been read.  But that space is given
to new processes when needed.  It seems that as much as possible is
cached into memory.
Alan