Hey, I've noticed this with three games now playing the 1.1 beta. I cannot have peace. It doesn't matter what I do, most nations are going to attack me pretty quickly. The AI setting is intelligent, however it doesn't seem to matter whether they can actually reach me or not (much of the time they are across the map with several empires in between)... they still declare war on me anyways. This hadn't happened in 1.0X, so I think it is new.
One thing that I have noted though, is that as a "-" modifier on the report screen is a "I know what you're doing" comment for everyone except the Terran Alliance. I'm not doing anything! I only have a couple of defenders per planet, and am focusing on peaceful development of my economy and starbases (two starbases per system... one economic and one military). These conflicts are indecive, and somewhat irritating given that neither one of us really has the potential to harm the other.
Just thought I would point it out as a possible problem in diplomacy weights, and say keep up the good work.