Thanks Chris ! I've made some edit in my previous post (you answered quicker than i thought ), and i have some weird new problems...
EDIT2 : ok, deleted ~scanboot.xml and Temp folder and scan worked. But another problem occured... I'm editing the REV category and i'm on the STN 3K, 5K and 6K. I'm editing this way : REV / STN / M3K or M5K or 6K (which i translate into the real hardware name with the dictionnary file). Well, the 3K and the 6K show well, but the 5K disappear completely, it is even wiped from my Temp folder :-/
I'm not sure really to be honest - why are you deleting scanboot xml? The only things I ever touch other than updating in NAT is to delete the contents of the temp folder whenever I add a new (edited) library.
I've had problems with NAT and editing in the past whereby I installed an update and then had things disappearing. Whenever an update comes up now I always do a completely fresh install instead of updating. The two things might not be linked though, I've just gotten into the habit of doing it.