Mine was kinda similar. Back when I was still a hopeless noob I was questing in ...Ashenvale I think (some elfy place) with my boyfriend and a guildy. A couple of PVP-flagged level ?? trolls were running around the place. I think it was the first time I'd seen any high level Horde players, and certainly the first time I'd seen anyone of the opposite faction flagged for PVP. I didn't really understand how it worked. So my boyfriend warns me "don't attack them!". I scoffed at him "well duh, I wasn't going to!". Apparently I didn't really get the difference between left and right clicking yet either, so I targeted one of the trolls and did a /wave at him. We then ran off to continue our questing. Or we would have done, but I gave the troll a good whack with my staff as we ran past. Panic ensued, we were dead within seconds, and the two Hordies followed us around slaughtering us and our quest NPC's until we gave up and hearthed :( I think it put me off PVP for life.
Also, just recently, I was running through the tunnel from Moonglade to Winterspring, on my way to do some grinding. I passsed a troll hunter on the way. He stopped, turned, looked at me...and the next thing I knew I was being charged by a boar. After a brief WTF? moment I gave in and died. I still have no idea how the hell I was flagged :(