How is Russia's current influence on those ex-Eastern Block countries in military aspects?

Do Eastern European countries still buy Russian weapons? or they have all switched to American stuff?

Also, many of those E.E countries are members of EU now, so are they allowed to buy Russian weapons?

Well the influence has lessened but is still there. Most of the equipment that is used is either Russian or Russian based although some countries do have a mix of both west and eastern weapons. I know that Poland has an upgraded version of the T-72 which has reactive armour and the such. Many countries have tried to make/design/produce their own assault rifles but many haven't succeded in donig so due to a lack of money.

Well there airforces have changed from mainly russian to using western equipment, Hungary and Czech Republic have both ordered Saab Gripens and Polands looking at F-16s. Poland has also ordered the finnish Patria AMV. Weapon wise in the army though they still mainly use russian technology though some such as Czech republic and slovakia have begun modernising vehicles such as the T-72 and some artillery systems are being changed from 152mm to 155mm. I think assault rifles are still all either kalashnikovs or copies of it, dont know if this will change soon as AKs are the foundation platform for most rifle designs in the world.