Hi,

this problem is getting worse the more masternodes are on v12.

I did a fresh startup, it took the node 6 minutes of 100% CPU load to parse through the complete masternode list

2015-08-27 08:37:27 Dash version v0.12.0.49-5410e0a (2015-08-25 13:39:04 -0700)

[....]

2015-08-27 08:43:40 CMasternodeSync::GetNextAsset - Sync has finished

At the time of startup there were 2638 masternodes in the list

~$ dash-cli masternode count
2638

debug.log contains 9922 occurences of

CMasternodePaymentWinner::IsValid - Masternode not in the top 10
and
mnw - invalid message - Masternode not in the top 10
each.

If old v11 nodes are the cause of this, this is a DoS attack vector. In either case: This should not happen :)