Works for me with: 7zip, the extractor Microsoft provides with Windows Vista / 7 / 8, and with unzip on linux.
**What program are you using? **
If using one of the above I would suggest: disabling any "download accelerator", re-downloading the zip archive, and trying to extract again.
If you are not using one of the above I would echo Steve's suggestion. Try using a different tool (if your OS did not come with an extraction tool, try one of the extraction tools listed here).
NOTE: I do know problems have been reported in the past unpacking the Edit Order's Zip archive using "NCH Express UnZIP". These were resolved by the poster using one of the recommended extraction tools instead of "NCH Express UnZIP". I believe the cause was "NCH Express UnZIP" not being able to handle extracting files where a "" is specified in the path (allowed by the Zip archive specification). Most GOOD tools will handle both without any issues. The packaging process used by Edit Orders has been modified in upstream versions to only use "/" for paths in Zip archives (as recommended in the specification to provide the widest platform independent compatibility).