I had a problem with my Clip+ that bothered me the last 2 months. I have the 8GB version with the Rockbox Version 3.10 running. Everything works fine when I added an additional 8GB microSD Card. But as I exchanged it with an 32GB Card I was not able to initialize the database. It randomly frooze after a few songs - most of the time between 600 and 1200. Around 2500 Songs are on the internal memory. Putting just a few songs an the microSD Card didn't help anything. The original firmware had no problems to build the database. It just took ages.
I tried to rewrite all MPEG headers, cut down the ID3 Tags, removed all the included covers. But nothing helped.
Usually I formatted the microSD Card with allocation unit size: default.
Yesterday I tried to format the Card with allocation size of 64k. And now it works perfectly fine and the database is build within a few Minutes.
Hopefully this information helps somebody. I looked hard to find a solution, but I found nothing on the internet. And it took my hours to try out everything.