R9 290 Is not getting any shares

Hello fellows!
I have a strange problem with my R9 290.
I am not getting any shares from my pool. It only says:
"Stratum from pool 0 detected new block" as if the vardif is too high, but my pool does not support vardif (?!)
My R9 280X works just fine on the same worker/pool.
And now to the strange part: When i put the intensity lower than 15 it works fine, but i don't want to do this because i lose 350 khash/s.
Can someone help me?

Code:

{
"pools" : [
	{
		"url" : "http://coinotron.com:3334",
		"user" : "Valansch.1",
		"pass" : "1"
	},
	{
		"url" : "http://coinotron.com:3334",
		"user" : "Valansch.2",
		"pass" : "2"
	}
]
,
"device" : "1",
"scrypt" : true,
"intensity" : "20",
"vectors" : "1",
"worksize" : "256",
"thread-concurrency" : "8192",
"shaders" : "2048",
"api-port" : "4028",
"gpu-threads" : "1",
"log" : "5"
}