found the bug.
it is actually caused by the 65k gold merchant bug.
when that occurs, and the player continues to barter, their mercantile stats break.
Yes, Living Economy's 65K bug may do that.
the work-around is:
1. keep an eye on the merchant's gold
2. when it becomes 65k, exit the barter screen
3. it is safe to buy/sell again from the dialogue screen.
but if this has been fixed in Enhanced Economy, its all good.

(i really have to install obse0018.)
Yes, Enhanced Economy has dynamic barter gold, and without any 65K bug. I can of course not guarantee that it's completely bug-free yet, but I found the cause of the 65K bug in LE, and am sure that I didn't repeat that.
For the MMM OMOD installer, when in your instructions it says "extract to a MMM folder on your PC", do you mean just make a folder and extract them there? Or am I extracting them into an already existing folder?
To any empty folder of your choice.
Also, when it says "No need to extract this folder" in your instructions, can you please explain what you mean exactly. Sorry for the questions, but I am rather excited about finding an easier way to install MMM alongside OOO.
I mean that you only need to download the archive and not to extract it with winrar, or whatever you use, e.g. just keep the .7z (or .rar) file on your HD without extracting it.
This is because OBMM has an "Add archive" function where you select such an archive. If you extract such an archive to a normal folder, you can use the "Add folder" command instead, but this is just an unnecessary step.
Also, in your instructions, when it says on number 12 where it says "in OMOD creator window click 'add folder'" what folder am I adding? The MMM one?
Ouch, an error has crept into the instructions at TESNexus. It is correct at the discussion thread http://www.gamesas.com/bgsforums/index.php?showtopic=995334 though, where it says:
11. In the "omod creator" window, click "Add folder"12. Choose your extracted MMM folder and click "OK"
So yes, you're supposed to add the MMM folder

It will be easier when the next full version of MMM is released, as the omod installation script is supposed to be included as part of MMM then.