The file can be converted from ASCII to BINARY using "fixgz." It can be found here: http://www.gzip.org/#faq1
The usage of fixgz is as follows:
fixgz nameofbad.tgz nameoffixed.tgz
As long as the file isn't truly corrupted, this conversion will convert the backups to BINARY, which can then be recognized and restored from the KACE Systems Management Appliance.