[CentOS] Mouse hour glass and desktop

What does it mean when your mouse hour glass pointer turns into
 a skull and cross bones symbol  for a few seconds and is then
 followed by your desktop icons being scrambled  around to 
 different locations.  This reminds me of a bug in the old
 Windows 98 SE desktop.
 
 What would cause this?  This has happened to me once before
 on Fedora 3 (I think, maybe 2).
  
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