The materials on that website are all user-generated so you will find different levels of organisation.
i have also found some work great straight off and some take a bit of fiddling.
Main problems are usually incorrectly linked files - so you have to go through and repick the texture files.
There's no real answer as the problems will depend on each texture creators methods.
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David Chappell
Freelance Motion Graphics / 3D
http://www.IncidentalTrees.co.uk