Here recently I was tasked with grabbing content from a client's production systems to install in our dev system so the developers could test their code against real conent without worrying about damaging production content should things go wrong in testing.

Everything went well until I tried to upload the package to our development instance of AEM, in which case I was met with this cryptic error message from CRX Package Manager:

After almost an hour toiling around with this error and expecting it to be a corrupted zip file I finally discovered the cause. The development instance was running a 32 bit version of Java by some oversight probably on my behalf. The environment that originally packaged the package was running 64 bit Java. To correct this and allow my package to be uploaded to the CRXDE Package Manager, I simply upgraded the development instance to the same version of Java (including making sure it was 64 bit installed). After bringing the two Java versions in line with each other I was able to upload my package and install it with no errors.