Is there any known issues imaging accross a 100mbit WAN connection? (Did a seach didnt find anything).

I got a call late today that some people at one of our sites tried to image a PC at a third site via our WAN.
They got to the point where it is copying image files accross, but taking in excess of 5 hrs or so instead of the usual 15 minutes.
Naturally the first thought was congested links, but they tested these and they have pleny of available bandwidth.

I havent had a chance to check and see that they have everything configured correctly, will do that in the morning.

So, any know issues imaging accross a WAN, or should it just work as per LAN?