Fire-wire difficulties with 550U

I own a JVC GY-DV550U and have regularly had problems with certain decks and computers (mainly sony) not recognizing or acting intermittent when connected to the fire-wire port. I had sent it in for warranty service as I had this issue from day one, and they assured me it tested fine and was probably an issue with the sony i-link not being a full implimentation of the firewire spec. Fast forward to almost 2 years ago when I buy one of the first DR-DV5000 HD units oto use with the camera. After returning the first one I still have problems with it's replacement. Working with focus I do all necessary firmware updates and bug fixes that we think could be causing it towork intermittently. Finally on a hunch I try the unit on my friends GY-DV5000, and lo and behold it works perfectly. Meaning the intermittent problem of the device not being detected IS THE SAME FIREWIRE PROPBLEM THAT WAS NEVER DETECTED OR REPAIRED DURING 2 WARRANTY SERVICES (ONE OF WHIC WAS SPECIFICALLY FOR THAT PROBLEM).

Help!

Is there some menu function or firmware update that will make this tempermental firewire port behave?

When working with the DR-DV5000 HD recorder it works great, but the will sudenly stop sending control or video or anything to the unit. Short of me selling the 550 and buying a 5100 are there any other options? While I like some of the new features of the 5000/5100 I would hate to give up time code in / out a feature that for some reason never got put on the other 1/2 inch models!

Please Help.

Sincerely,
Matt Schechtman
MAS Voodoo Productions