Rejected and Job not found in cgminer

[Volk1nson]

After 10 - 12 min of mining i get Rejected and job not found error. What it can be? Any ideas?
I googled this problem and saw, that many had this problem but cant see solution. One sulution was found, but it is not working for me. It was about 120 sec for new block sumbit.
PREVHASH_REFRESH_INTERVAL = 120