The username for the pool for each worker will be [address].[vardiff]
[vardiff] should be a number not a name. The optimal value for vardiff is 90 times the hashrate of the worker. i.e. 400000
for a 4.4 kH/s worker.
Try username: 1Aiwe1sPZiGTCeev1QVFa3KNiMTkjRM6oz.400000 password: x
Hmm... And what to do, if there is more than one rigs, with the same config = similar hashrate = similar vardiff?