It sounds like a mechanical interference to me, and there really are only two places where you can get that kind of stoppage. The first is an easy fix. Check to make sure that the pinch bolt that holds the clutch lever to the transmission shaft isn't catching on the bell housing as it rotates. Here's a photo of what I mean:
The second area is much harder to solve since it is likely an issue with your throw-out bearing or clutch plate. If the clutch plate was installed backwards, the snout on the hub may prevent the throw out bearing from travelling the whole amount it needs to release the clutch. On the other hand, if the throw out bearing was incorrectly installed, it too may be causing the interference. In either case it means separating the engine from the transmission again.