1) pipelines goes through Ukraine and Poland, if Russia attack (militarily or otherwise) these countries, oil to EU stops. Why do you think Germany is rapidlly building pipeline from Russia going under Baltic sea?
2) not long ago defence shield has been viewed in US as something which is not needed and the talks went slowly. On the other hand many people in Poland viewed the balistic missiles stations as something they do not need because there is NATO. Russian troops in Georgia changed all that.
3) Russia is objecting to the shield mainly because it will be build in countries that they feel should be in their sphere of influence. It does not matter that Poland is in NATO or that Ukraine or Georgia want to be in NATO. Many people there still think of Georgia or Ukraine as of their own republics and about Poland or Hungary as of the countries which should be under their influence. It is not a COLD WAR it is russian feeling that “these countries belong to us”
4) In Georgia as well as in Ukraine there is a large number of Russians. In Georgia these Russians are conflicted, many of them do not know what to do and in these conflict russia counted on their support. I think it badly miscounted. On the other hand in Ukraine in Crimea there is large population of russian who do support all things Russian – a little bit different situation from Georgia.

Just my two cents.