I am experiencing the exact same issue. Although I took advantage of the preload option as soon as it was available, I ended up buying the retail copy of SiN Episodes: Emergence. Once I came home and started up Steam I got a window saying it's "Validating SiN Episodes: Emergence File 1 out of 1" but it almost instantly disappears, and then in "My Games" it shows SiN Episodes: Emergence as "Downloading: 50%" even though, as Indy pointed out, the Steam Bandwidth Monitor shows no activity whatsoever.
I would would be very grateful for any insight or advice as to how this issue can be resolved. I read and followed the suggestions in the Sin Episodes Pre-Start Checklist
. In the first post Michael Russell says that "we've seen a 3-4fps boost by waiting for the preload to finish," so I'd like to find a way to get the preloaded content to work if it will yield greater performance in game. However, if nothing else works, I'm assuming that this can be resolved by simply deleting the local SiN Episodes game content that I have preloaded and then installing the game off of the disk I got at GameStop.
Any response is greatly appreciated.