I am having this problem when downloading themes. It does not matter which theme is downloaded. I get "unexpected end of archive" when opening the file. This started for me late last night and thought it would work today. I am updating multiple websites and need to download many themes. The first time I tried today it worked, yet every attempt since did not work (even if trying the same theme that worked previously.)
I have tried multiple browsers, cleared cache, and used multiple programs to unzip.
Thanks in advance.