[RESOLVED]I am trying to send ether from Account1 in Node1 to Account1 in Node2, both Node1 and Node2 are running under same network ID. I am able to send ether between accounts in same node but not between different accounts in different nodes. Error is "No key for given address or file".
Since you are running 2 different nodes and it works on 1 node but not on the other, I'm guessing that you don't have a miner running.
Make sure you are mining on that network, otherwise the nodes won't be able to verify transactions with each other.
On the production network other people are mining for you, but on your own test network you have to supply your own mining cycles.