Here are most common issues:
1. Please check if date and time are correct on your mining rig.
2. Probably your miner messed something with DAG file.
Stop miner, delete all DAG files and restart miner.
On Windows you can find DAG files located in the AppData / Local / Ethash folder under your computer’s Username in the Users folder (example: C:/Users/myPC/AppData/Local/ Ethash). You may need to enable the showing of hidden system files first in order to see the needed folders in Windows Explorer if you have not enabled it already.
3. Wrong version of GPU drivers:
The solution is to download and install the AMD 15.12 driver. Uninstall of 16.3, run CCleaner to cleanup leftover registry entries, restart, and then install 15.12
Here is solution. Please start ethminer this way:
You can put it all in a bat file.
setx GPU_FORCE_64BIT_PTR 0
setx GPU_MAX_HEAP_SIZE 100
setx GPU_USE_SYNC_OBJECTS 1
setx GPU_SINGLE_ALLOC_PERCENT 100
ethminer ...blablabla...usual...stuff.... --cl-extragpu-mem 0