Frpm looking at the nut, it does look like the front is higher than the back of the slot for the high E so it looks like it could be that.
What is involved in sorting that out? Is tehre special files or anything?
If I have to change the slot, is it worth putting a new, decent nut in there instead? If so, whats best - bone, graphite or something else entirely?
Cheers'an!