How do i know, that my wallet works fine?
As long as you do not receive any connections errors, you should be fine for mining.
Also, make sure both your bitcoin and creditcoin blockchain are in sync by looking for the two green check marks at the bottom of your client. Check the photo.
Yes, both in sync and both green check marks are green, i wonder how long that take to get a "reward"!?
edit:
here some errors from the debug.log
2015-05-01 09:06:24 ERROR: Bitcoin: AcceptToMemoryPool : nonstandard transaction: dust
2015-05-01 09:06:33 hashmeter 737096 hash/s
2015-05-01 09:06:34 ERROR: Bitcoin: CheckTransaction() : vin empty
2015-05-01 09:06:34 ERROR: Bitcoin: AcceptToMemoryPool: : CheckTransaction failed
2015-05-01 09:06:34 Bitcoin: Misbehaving: 217.23.12.108:8333 (70 -> 80)
2015-05-01 09:06:34 ERROR: Bitcoin: AcceptToMemoryPool : nonstandard transaction: dust