http://forums.kc-mm.com/index.php?topic=2913.0Read his Final Notes (in red)
apparently too many portraits cause freezing.
I would think it's the file size, but I wouldn't know since I don't have my portraits.
So for everyone having problems freezing while importing your portraits I would recommend
replacing each portrait one by one using a different formatting than "C18" maybe "CMPR" since I believe "CMPR" don't require a separate palette meaning less of a file size, but I don't know I'm no expert at this, that is just what I believe could work, also make sure to use indexed images for your portraits.
For those of you who don't know what I'm talking about when i say "C18" or "CMPR" they are image formats used in BrawlBox, when you try to replace any image a box will pop out and you can change the format there it will also tell you the data size for each format so try the one with the lowest size.
I can confirm that it's the size that's causing the problem. When you import the original portraits, the size goes up a lot, putting it higher than the original file. I had to take out a lot of stuff to get it to work again (I got rid of all that Wi-Fi text, and the Japanese characters that is supposed to come up when you make a name(done by replacing the pics w/ a 1 pixel pic)).