Here I ran some in-depth tests between different fast download URLS on different web services.. including my VPS.
So generally across ALL fast dl urls.. it happened atleast once on random maps that need to be downloaded.
Reloaded CS and it downloaded them fine.
I'm not running any crazy maps that aren't known.. so Idk why this issue could be going on honestly.
BTW I noticed if you download a map it goes into cstrike_downloads, and if you delete the map from cstrike_downloads without reloading cs 1.6 you can replicate my error. Of course, In this case people aren't really deleting anything.. they just can't download it from the start lol.