I apologize if this is the wrong place for this but I just had a really strange thing happen.
Overnight Kontakt or something (Windows maybe, don't see how it could be SONAR) changed the file path for my NI sample libraries.
The libraries are on an external drive labelled F:
The file path was changed to a drive labelled L: (I don't have an L: drive on my system)
I can change the file path back to F: but it's a pain in the backside; I have to do it manually for every library I have (about 14) and I will apparently have to do it for every project that uses Kontakt.
Anybody else ever seen this?
 

I've seen Windows change drive letters for seemingly no reason. Maybe after a boot there was no drive F: (e.g. a removable device was plugged in at boot time and subsequently removed) and Kontakt got confused? I've never seen this behavior, but then I've never run libraries from an external drive.

Certainly it is some Windows bug or some configuration problem of your drive.
But you can quickly convert to the new path using Kontakt's "Batch re-save" function.