I'm having a rather annoying issue with the http://download.fliggerty.com/download--22, regarding the key for Lower Arkngthand. It seems the mod does not like keys with weight. Whenever you look at a door, chest or NPC the mod adds the keys into your inventory, which is an extra 50 pounds for that one key. So I dumped the key from my inventory and subsequently shed 50 pounds. However, the key is still attached to the keyring. This allows for an exploit - for testing, I dumped my entire inventory, including the keyring, into containers and found that my encumbrance was negative (adding things back to my inventory kept the number at 0).

So I have two questions:

Is there a command I can use to reset my encumbrance back to 0?

For anyone using this mod - is it possible to remove keys from the keyring, so that I can dump the Lower Arkngthand key when I'm done with it? If not, how would I go about resetting the mod entirely?

I like Manauser's http://webpages.charter.net/manauser/morrowind/#toolkit

console command:
startscript tkWeightFix

This is really odd... I have not used the keyring mod myself yet, but as practically all keys from the original game and the expansions have zero weight I thought that that would be the case with keys from mods, too. It was not until a few weeks ago when I realized that this assumption was wrong and I rid myself of more than 100 pounds of old keys, including the 50 pound key you mentioned. But that was only after I had carried them around for 100 hours or so...

Regarding the second question, I RTFM (again) and fixed that one, but that toolkit is nice.

The UESP says that all keys are weightless (lies) but the Arkngthand one can't be the only one, surely?

Well, most keys are weightless. And Arkngthand key is the only one with such significant weight IIRC. I'm not sure if ALL others are wightless, though.

I loved the keyring mod, but I had to get rid of it because of similar issues. I believe there were problems with scripts not detecting the keys in your inventory, as well.