Allroad, glad to hear you found the problem which was smililar to mine.  Whe the noise was happening to me, I just could not ride my bike hard with the noise.  I had to slow down, I just did not want to futher damage what ever was wrong.

I have just encountered the same problem myself. I have the same wheels and could have sworn the noise was coming from my bottom bracket. 

Took it to the local bike guru who couldn't replicate the noise, but suggested straight away it was probably the rear hub - well he said bearings. So i took his advice and put some spare wheels on and hey presto no noise coming from the bike. 

How did you get it fixed.  Sounds like another design flaw from Easton.  I'm about to give up on them.  I've had problems with their former Easton Orion II's and Easton Ascent II's and now this with the Easton EA90's SLX's!  

Saul,

The problem was cured by tightening the alloy cassette body on the rear hub. The cassette body is the splined part that slides over the rear hub and adapts the hub to Shimano or Campagnolo cassettes. The shop tightened mine and also lubed the hub bearings, which quieted the loud ratcheting noise in the hub. Hope this helps.

allroad:

Saul,

The problem was cured by tightening the alloy cassette body on the rear hub. The cassette body is the splined part that slides over the rear hub and adapts the hub to Shimano or Campagnolo cassettes. The shop tightened mine and also lubed the hub bearings, which quieted the loud ratcheting noise in the hub. Hope this helps.

In my case, the problem with my HED Bastogne was not the cassette but the hub itself.  I moved the cassette (Sram Red 11-26) over to another wheel and no noise.   We also tighten the cassette on the HED and it still made noise.  I'm expecting a new rear wheel of HED anyday now.  My LBS took forever to send it to HED and never checked on HED to get a replacement.  ;<(  I had to use my cheaper wheel for over two months!  I only had the bike since middle of May!

I may not have been clear about what was causing the tickety-tack noise in the rear hub. It wasn't the cassette or the hub. It was the Campy specific cassette body that slides over the drive-side body of the hub to allow the use of a Campy cassette. (There is also a Shimano specific cassette body that adapts the hub to a Shimano or SRAM cassette.) The Campy cassette body wasn't tight enough on the hub and when under load, slipped back-and-forth enough to cause the noise. It's an easy and quick problem to correct after the cassette is removed. Sorry for the confusion. Hope this helps.

i was having simular issues with my R3 SL, with FSA cranks [cranks are weak]. come to find out... it was the pedals. 

I think the take-home message for everyone is that with bike frames - especially aluminum and carbon - the tubes can really cause the sound to come from funny locations (like the bottom bracket) when the sound is actually coming from somewhere else.  (This effect is even worse with the monocoque carbon frames these days as the carbon even seems to amplify the sound.)

Some of the best advice here came from the friend with 25 year's experience: rather than listening to where the sound is coming from, try to find out what activity seems to cause it (standing, sitting, sprinting, spinning, high power, low power, etc.) and start your elimination on what that reveals.  I've even spent months searching for noises that I thought came from cranks or pedals which turned out to be creaking in the front fork dropouts!

Good luck!

I had intermittent creaking when in high torque situations. Found out it was my stinking cf bottle cages slightly loose.