Made an account just to post this: this thread helped me out! I was early enough in the game where it wouldn't matter if I had to restart without a backup, but this saved me time hah.
I wouldn't have thought that messing with WonderCards would impact my pokemon boxes but it did. So my game would crash when moving a pokemon from my party to the box.
I'm not sure where the corruption was, but I went ahead and just cleared most of the boxes. I did 6 and 7 first since people mention it in this thread.
I was using PKSM, not Pokegen so I wasn't sure if this info would apply to me (I had no error code) but it helped!
Thanks.
This helped me a ton. I wouldn't have thought to clear boxes 6 & 7 when my issue was occurring when I was in box 1. I am playing Black 2 and this thread still helped. Great guide, found it through another thread on Google.