The problem appears to be some version mismatch in the used XML libraries - I have no clue yet what caused this. But I have added code to my build (it is number 290 right now) to catch the problem and to ignore the old downloads.dat file in this case. You will have to go to the library windows and resume the partial files by hand.

Do you folks with the problem have by chance a xerces.jar in /Library/Java/Extensions or in a similarly named Folder in your home directory?