You see a BlockStoreException very occasionally when MultiDoge starts. It prevents you synchronising with the Dogecoin network.
You can fix this problem by doing the following:
Find where MultiDoge is storing your user data - see the help topic Troubleshooting
Shut down MultiDoge
Go to your MultiDoge user data directory - worked out in step 1 - and delete the file multidoge.spvchain
Start up MultiDoge again