My birdog has the exact same problem - turn it on not even attached to lnbf and I2C error appears and dotted line comes on display and then it is totally nonresponsive. Sometimes if I let it sit for a few minutes it comes back on. Other times I have to disconnect the wires to the battery and plug them back up only to have the meter reset and the battery showing 0% charge.
Anyway, I contacted the birdog people several times and basically got a non-answer as to the possible cause, but they gave me the contact info for the company that does repairs:
Pacesetter
400 Trade Center Dr
St Peters, MO 63376
1-800-963-6363 ext 220
They will give you an RA# and have you ship them your birdog for repairs. If it's still under warranty they will fix it for free. Otherwise they will call you back before fixing it to advise the cost, and if no problem is found they will charge you $45 for their trouble. I shipped mine to them about a week ago and haven't heard back just yet - I'll let you know what they say. Luckily I have a friend not installing anymore who loaned me his birdog for now. If you don't have your meter how the hell are you supposed do your work, spend another $400 to have a backup birdog? Hope this helps.