http://www.icyphoenix.com/viewtopic.php?f=35&t=4344&p=29698#p29698
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Mighty Gorgon
Thu 10 Jul, 2008 13:08

Re: Attachments Invisible
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If attachments are images your serve may limit CPU usage when generating thumbnails and you can face that problem.

Try to disable thumbnails in attachments and verify again.