I have MacPros 1,1 and 5,1 at work and neither can reliably connect with FireWire on two 722s. A MacbookPro and iMac with Thunderbolt adapter work fine, so I had to give up on FW with these MacPros and went to CF cards and card readers. I feel the FW chipsets in these must be different. This is with OS10.6.8 on the 1,1 and 10.9.5 on the 5,1. Before 10.6.8, the 1,1 wasn't too bad at connecting.
Sound Devices had nothing helpful to offer on this problem.
So, do you have a MacPro desktop or a MacBook Pro laptop, and what model?