diff --git a/src/main.cpp b/src/main.cpp
index 0d79246a1..16d1cba6e 100644
--- a/src/main.cpp
+++ b/src/main.cpp
@@ -2243,8 +2243,7 @@ bool ReceivedBlockTransactions(const CBlock &block, CValidationState& state, CBl
     if (!pblocktree->WriteBlockIndex(CDiskBlockIndex(pindexNew)))
         return state.Abort(_("Failed to write block index"));
 
-    // New best?
-    return ActivateBestChain(state);
+    return true;
 }
 
 
@@ -2520,7 +2519,6 @@ bool AcceptBlock(CBlock& block, CValidationState& state, CBlockIndex** ppindex,
     }
 
     int nHeight = pindex->nHeight;
-    uint256 hash = pindex->GetBlockHash();
 
     // Check that all transactions are finalized
     BOOST_FOREACH(const CTransaction& tx, block.vtx)
@@ -2593,10 +2591,11 @@ void PushGetBlocks(CNode* pnode, CBlockIndex* pindexBegin, uint256 hashEnd)
 
 bool ProcessBlock(CValidationState &state, CNode* pfrom, CBlock* pblock, CDiskBlockPos *dbp)
 {
-    AssertLockHeld(cs_main);
-
     // Check for duplicate
     uint256 hash = pblock->GetHash();
+
+    {
+    LOCK(cs_main);
     if (mapBlockIndex.count(hash))
         return state.Invalid(error("ProcessBlock() : already have block %d %s", mapBlockIndex[hash]->nHeight, hash.ToString()), 0, "duplicate");
     if (mapOrphanBlocks.count(hash))
@@ -2665,7 +2664,11 @@ bool ProcessBlock(CValidationState &state, CNode* pfrom, CBlock* pblock, CDiskBl
         mapOrphanBlocksByPrev.erase(hashPrev);
     }
 
-    LogPrintf("ProcessBlock: ACCEPTED\n");
+    }
+
+    if (!ActivateBestChain(state))
+        return error("ProcessBlock() : ActivateBestChain failed");
+
     return true;
 }
 
@@ -3101,6 +3104,8 @@ bool InitBlockIndex() {
             CBlockIndex *pindex = AddToBlockIndex(block);
             if (!ReceivedBlockTransactions(block, state, pindex, blockPos))
                 return error("LoadBlockIndex() : genesis block not accepted");
+            if (!ActivateBestChain(state))
+                return error("LoadBlockIndex() : genesis block cannot be activated");
         } catch(std::runtime_error &e) {
             return error("LoadBlockIndex() : failed to initialize block database: %s", e.what());
         }
@@ -3230,7 +3235,6 @@ bool LoadExternalBlockFile(FILE* fileIn, CDiskBlockPos *dbp)
 
                 // process block
                 if (nBlockPos >= nStartByte) {
-                    LOCK(cs_main);
                     if (dbp)
                         dbp->nPos = nBlockPos;
                     CValidationState state;
@@ -3919,10 +3923,12 @@ bool static ProcessMessage(CNode* pfrom, string strCommand, CDataStream& vRecv)
         CInv inv(MSG_BLOCK, block.GetHash());
         pfrom->AddInventoryKnown(inv);
 
-        LOCK(cs_main);
-        // Remember who we got this block from.
-        mapBlockSource[inv.hash] = pfrom->GetId();
-        MarkBlockAsReceived(inv.hash, pfrom->GetId());
+        {
+            LOCK(cs_main);
+            // Remember who we got this block from.
+            mapBlockSource[inv.hash] = pfrom->GetId();
+            MarkBlockAsReceived(inv.hash, pfrom->GetId());
+        }
 
         CValidationState state;
         ProcessBlock(state, pfrom, &block);
diff --git a/src/miner.cpp b/src/miner.cpp
index ddd277a9b..baaa22c8f 100644
--- a/src/miner.cpp
+++ b/src/miner.cpp
@@ -484,22 +484,22 @@ bool CheckWork(CBlock* pblock, CWallet& wallet, CReserveKey& reservekey)
         LOCK(cs_main);
         if (pblock->hashPrevBlock != chainActive.Tip()->GetBlockHash())
             return error("BitcoinMiner : generated block is stale");
-
-        // Remove key from key pool
-        reservekey.KeepKey();
-
-        // Track how many getdata requests this block gets
-        {
-            LOCK(wallet.cs_wallet);
-            wallet.mapRequestCount[pblock->GetHash()] = 0;
-        }
-
-        // Process this block the same as if we had received it from another node
-        CValidationState state;
-        if (!ProcessBlock(state, NULL, pblock))
-            return error("BitcoinMiner : ProcessBlock, block not accepted");
     }
 
+    // Remove key from key pool
+    reservekey.KeepKey();
+
+    // Track how many getdata requests this block gets
+    {
+        LOCK(wallet.cs_wallet);
+        wallet.mapRequestCount[pblock->GetHash()] = 0;
+    }
+
+    // Process this block the same as if we had received it from another node
+    CValidationState state;
+    if (!ProcessBlock(state, NULL, pblock))
+        return error("BitcoinMiner : ProcessBlock, block not accepted");
+
     return true;
 }
 
diff --git a/src/rpcserver.cpp b/src/rpcserver.cpp
index 72a7fe83e..d4ceb7f99 100644
--- a/src/rpcserver.cpp
+++ b/src/rpcserver.cpp
@@ -254,7 +254,7 @@ static const CRPCCommand vRPCCommands[] =
     { "getblocktemplate",       &getblocktemplate,       true,      false,      false },
     { "getmininginfo",          &getmininginfo,          true,      false,      false },
     { "getnetworkhashps",       &getnetworkhashps,       true,      false,      false },
-    { "submitblock",            &submitblock,            false,     false,      false },
+    { "submitblock",            &submitblock,            false,     true,       false },
 
     /* Raw transactions */
     { "createrawtransaction",   &createrawtransaction,   false,     false,      false },