Ah possibly true, but I didn't think that the NT logon token was passed all the way down to MSAS. I had a suspicion that the WCS credentials were used for the MSAS roles.
Now given the problem as originally described is that the dimension order has reverted to what is the original CAR file rather than the view. The only way I can see that the set generation is causing it is if it fails to create the set in the view then it reverts to the base CAR file. This is possible but I don't see why the original set is visible if the reordered one is not.
Another thing to check is that the administrator (using Enterprise authentication) sees the reordered set when they reopen the view. Also try changing something else, like a slice member, then see whether the view is actually totally the base CAR file or whether it is mixing and matching from the saved view and the base CAR file.