Just to add a bit to the good stuff that's already been posted:
1st, if you haven'y already, eliminate ( bad pun
) potential physical cause(s) w/ a vet exam. If your dog is overly excitable, your vet may be able tp prescribe a "doggie downer" for anxiety/hyperaction.
I believe you definitely need an outside evaluation of your relationship with your dog. A behavioral assessment by a professional trainer may identify cues that you may be giving your dog that signal the onset of fearful submission stress in her or aggressive protective action. Then you can identify those triggers and instead work on actions/methods that encourage calm submissive behaviors.
In one instance I helped with, an owner would come home after a tough day at work to a dog that was 1) overjoyed to see her, and 2) had been in the house all day and HAD TO GO! The dog would come greet the owner, jumping on her work clothes which caused the owner to give an angry NO!
and pushing the dog back. The dog then peed in the entry way which further pissed off the owner even more. Vicious cycle.
At other times, owner would come home in good mood or grubby clothes and encourage an enthusiastic greeting, also giving the dog one of her own.
The inconsistency of allowing jumping up at some times, but not others, was confusing the dog. The dog never knew what to expect from the owner while it was messaging "I LOVE you! I MISSED you! i've GOT TO PEE!"Working on the owner to stop allowing the jumping up came first, & then to greet the dog in a calm, positive manner each time also sent a more uniform cue. It's not easy in our modern world but greeting her dog at a neutral "5"instead of an "8" one day and a "3" the next helped in this case
Lastly, I'd highly recommend The Dog Listener: Learn How to Communicate with Your Dog for Willing Cooperation by Jan Fennell
It should be in your library system or it's available through Amazon http://www.amazon.com/dp/0060089466/?tag=googhydr-20&hvadid=21390703447&hvpos=1t1&hvexid=&hvnetw=g&hvrand=5110300314961165&hvpone=11.55&hvptwo=&hvqmt=b&ref=pd_sl_8qf5o6uzfk_b
as well as http://www.janfennellthedoglistener.com/
There is a really good chapter in there on how & when
your dog is allowed to approach outsiders - strangers/guests.
Good luck, I hope this helps. Fell free to PM me if you want.