I'm unable to mine with spreadminer, either on Windows or the one I built Linux against the wallet. I get the same error with different nonces on both OSes:
Linux, I built (same error, over and over):
[2018-04-01 13:28:00] GPU #0: found a solution, nonce $00000000
[2018-04-01 13:28:01] GPU #0: result for nonce $00000000 does not validate on CPU!
Windows, prebuilt binary (same error, over and over, same nonce):
[2018-04-01 13:32:21] GPU #0: found a solution, nonce $000F4240
[2018-04-01 13:32:21] GPU #0: result for nonce $000F4240 does not validate on CPU!
I'm not seeing evidence that they are connecting to the daemon, but my ~/.simugames/simugames.conf looks like:
rpcuser=user
rpcpassword=pwd
rpcport=41677
daemon=1
listen=1
rpcallowip=127.0.0.1
rpcallowip=10.0.0.15
Which version are your NVidia Drivers?
If you mine on windows this is important, because the pre-built GPU-miner-binaries (built by tsiv) that we linked won't work with a newer NVidia Driver.
Shouldn't have an effect on linux though.