Update: Konami will post an update on the situation at 4pm today.
Original story: Konami has issued an apology for the ongoing issue with the Xbox 360 PES 2014 Data Pack 1.00 installation and the resulting inability to play online.
"We are aware that many of you are experiencing trouble getting online in PES 2014," wrote Konami. "Data Pack 1.00 needs to be installed before you can play online and there is an issue with the installation of this pack resulting in the error message 'The downloaded file is broken' at around 50% of installation.
"We are very sorry for this and we are working hard in collaboration with Microsoft to fix this issue and get you on the field as quickly as possible."
An update posted yesterday afternoon added that the publisher is "still in discussions with Microsoft trying to understand what might be causing this".
Some users have had success by re-downloading and installing the Data Pack.
An update on the issue is expected imminently.
Source: Konami via Sportra