Im getting the same error but only for tekkit lite. It retries the connection but they fail too. Must be something to do with the 0.5.2 update/all new updates. I dont want it yet i like my redpower so its not a big deal for me i just manually selected 0.5.1 and im playin as i type. The error logs look the same from the skim i gave them i can post it if you guys really want.
Edit its anything that has an update available and tries to update so its on their end.... i think