I have been mining for a while now. I restarted my computer this evening and I have been receiving the error " DAG Generation Failure. Reason: Invalid argument" when running the same bat file I always do. I have not made any changes to my system.
The following solution worked for some Reddit users
[–]avazawr... try to use parameter --no-precompute. It helped me
[–]Chadington1... Thanks! It worked for me too.
And this solution worked for someone on the Ethereum Forum
Bakoo13 Put the --no-precompute command at the end. If this doesn't work anymore (worked for me for 2 days), try the claymore miner. I'm trying it out now, too, and it seems to work more stable.