APBackup users often report of creating archives of over 4 gigs in size that appear corrupted.
In fact, the archives are totally fine. The problem is caused by the Zip64 format used by the program.

The problem is that the standard ZIP format has a number of limitations due to the 32-bit representation of the data block defining the archive structure (the size of the source file and the archive itself should be less than 4 gigabytes, the number of archived files should be less than 65535). These limitations are removed by Zip64, an extension of the standard ZIP format.

Whenever the size of the archive exceeds 4 Gb (or any limitation imposed by the standard format is reached), APBackup created a Zip64 archive.

Zip64 is currently supported by the latest version of 7Zip, WinZip and WinRar. If you try to open such an archive in earlier versions of these archivers (e.g. winZip 7.0), you will see a corrupted archive error. That’s why you should use the latest versions of archivers supporting Zip64 with files of over 4 gigs in size.