I've just done a first pass of 8900 files myself.
I'd echo the advice of not doing too many at a time as I got froze out at the point of saving if I tried to creep the wrong side of 450 songs at a time and I'd definitely suggest trying to move songs around to get the gold discs, then remove the empty folders from the right side (I'm working on the assumption that this frees up some more memory, though it also looks tidy ) and then try saving again.
As I got down to the last few hundred, I kept getting frozen out at much smaller numbers.
I worked out that I each time I got frozen out I had been dragging the same few albums in. I avoided these albums and then as I got to the last 100 songs went 1 album at a time. It was 1 particular album that Picard didn't like, my media players didn't like that album so much either so I wagered it was somehow corrupted. I deleted the MP3s just for that album and re-ripped it. Then it seemed OK.