Can't move blocks in Drupal 7 I currently have a site that has quite a lot of blocks (about 120 in 1 region and many others in other regions). 

Recently the Block admin page stopped working for me. I can't add any blocks through that screen, however when I go to the block detail page, I can.

All new blocks are handed the weight 0, and I cant change that (not by drag and drop, neither by manually entering the weight).

Anyone who know how I can fix this? Is it because there are too many blocks?
120 blocks in one regions seems to be excessive, you may want to attempt to consolidate them into a custom block and use context to set those.  Also may want to look at creating multiple regions that reside in the same area