have same problem with different browser , it's site problem.
I was thinking of opening a similar thread but waited thinking they was updating it for DK
I tryed to bypass loading pac-man did some collection edits and saved, it overwrited my collection but worked :) ( so don't do it ), so it seems like it can't load old user collection before editing.
I think the collection is one of best site functions , it let you find decks you can create , HSrep is done better but miss all the fun/meme decks this community have.
The current collection manager is done very well , but i feel like it use alot of site resourcers (image loading at first ) , so mb instead of remove it try create a simple version of it