For some reason, obj values 4 and 5 don't save over hotboot when inside containers. Index values save just fine, and the individual items save in inventories/rooms, but if they're in containers they reset to 0 for some reason.
I can't think of any reason why being inside a container would matter. fwrite_obj shouldn't care when it's writing the data. So the link should be what you want.
Thanks a lot for the fast reply - it was indeed the problem.
I glanced at that earlier, but assumed it was for area_vers, which is already at 4 in my mud :P
Odd that it only happened on objects in containers, though.