When I search with RCT2 and tracks/scenery checked, and try to sort by downloads ascending/descending, it'll throw me to a white page that says:

Server error

500
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The website encountered an error while retrieving http://rctgo.com/downloads/search. It may be down for maintenance or configured incorrectly.
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But the other forms of sorting work just fine.

I would let Justin know in an email to him.

I can't seem to reproduce this error -- exactly what are you trying to search for? (keywords, author, exactly what is checked/selected, etc.)