This morning at 06:13 UTC, the version 3 softfork activated at block 1032512 (
From this point on, all version 2 blocks will be rejected from the network because they can contain less secure transactions. Version 2 blocks are mined with Dogecoin Core 1.8.0 to 1.8.2.
If you're still running an old Dogecoin Core wallet, you would save yourself a lot of trouble (it might take longer for your transactions to be fully confirmed and if you relay too many invalid block, newer nodes might ban you) if you're updating asap to version 1.10.0.
If you have problems with 1.10.0, please let us know by creating an issue report on github, so that we can investigate. If you have heavy issues and you cannot run 1.10.0 at all, you could run version 1.8.3 in the interim, but that release is planned to no longer be maintained except for critical consensus issues. (And with this softfork gone well on there, it's very unlikely that we will do any maintenance on this version from here.)
^(* = may still receive version 2 blocks, be careful with confirmations)
With this critical consensus issue out of the way, we are preparing some optimizations on 1.10 in a minor release that should make it run even smoother (and hopefully consume less memory.) We will update everyone here once we know more about how that's going to look.
TLDR: Happy forkening, shibes! :)