Somehow files were corrupted before they got to my box. This goes for dumping using PMA as well as the WP-DB-Backup plugin.
Tested dumps made them with hexdump on got:
mymbp:Backup me$ hexdump -C file.sql.gz | head
hexdump: file.sql.gz: No such file or directory
hexdump: file.sql.gz: Bad file descriptor
Tried gunzipping .gz files in terminal and got.
gzip: /Users/me/Webdesign/folder/backup/file.sql.gz: not in gzip format
. This happens often when making a dump on a server that is located several 1000 miles away. They were corrupted during transfer. When I use WP-DB_Backup and e-mail the SQL dump all is well and the files can be gunzipped or unzipped without any issues.