I recently switched CDKEYs and experienced a bug involving the /c haks on function causing crashes. Basically, haks were enabled with my previous CDKEY and my character had some items in inventory that required haks. When I attempted to login to him I would crash loading the area. I fixed this by setting /c haks on with a different character that did not require haks. This appears to be because even though my associated CDKEY changed, it did not carry over my hak settings.
When you set haks on, you set them on for a cdkey / user in general. Unless you turn them off, you will need to have all the haks and what not to get back in. If you change keys, yeah, it will bring problems, and is no bug. It is simply the system.
Don't go changing cdkeys around and without notifying us, as we have systems in place that will rely on them. You really should have no real reason to change them unless you somehow lose the old ones.
I did lose them when my gaming laptop was destroyed in a flooded car.