Hope have got a great how to Video on there website
http://www.hopetech.com/page.aspx?itemID=SPG219
about half way down the page called
How to – Rebuild a rear Pro2 hub
have a quick watch and see if anything strikes you as being different.
The freehub is held in place by the end caps which hope call the drive side and non drive side spacers (from diagram above). These are normally quite a tight fit with the o-rings contacting on the axle (hence removal using a vice). Also when the hub is in the frame these will be held in compression by securing the wheel.
Did you use the hope tools for assembly or sockets? There is a possibility that the one of the bearing in the hub is not seated properly causing the axle to bind.
Also if you click on the pic foxy posted there is step by step instructions on servicing the hub.