user1087: I hadn't started/used my Bitcoin client for ages. Now, whenever I start the client, it is downloading block 135407 and does not progress past it.
What can I do?

user10084: I had a similar problem, but the -rescan option didn’t help.
In my case, there were a lot of lines referring to orphan blocks in my debug.log file (not 100 % sure it’s related but it may):
2014-08-18 20:52:57 ProcessBlock: ORPHAN BLOCK 0, prev=00000000000000001132f6ac32387e51960e3154b2ad4420bdeb64d77999388f
2014-08-18 20:54:00 ProcessBlock: ORPHAN BLOCK 1, prev=00000000000000000e9926124cabed78be0ae8bab22fb20acc643e94749120f8
2014-08-18 20:56:37 ProcessBlock: ORPHAN BLOCK 2, prev=00000000000000001b3f790fc107051c17702d305b08a3ae6325f40ecf44eae9
...

Finally, I tried to restart the client with the -reindex option which fixed my problem (but took 100 % of my CPU usage for several hours while reprocessing the blockchain).
So if the rescan option don’t work, don’t give up, try the reindex option!

user1087: Okay, based on the comments I have tried a couple of things but in the end only the following worked:

Close Bitcoin client
Backup files from %APPDATA%\Bitcoin
Optional:Download Block chains from:     http://sourceforge.net/projects/bitcoin/files/Bitcoin/blockchain/ to prevent lengthy initial download (Warning: the link advises against doing this if you have transactions in your wallet).
Start Bitcoin client with the
-rescan option from command line. 

After that the client started downloading blockchains again. This worked for me. Not sure if this will work for everyone.

user3668: I had this happen to me once. It was apparently caused by an incompatible peer node. 

Delete $HOME/.bitcoin/peers.dat
Restart bitcoind

Afterwards, new compatible peers will be found, and hopefully, you'll start processing blocks as expected again.

1087: <p>I hadn't started/used my Bitcoin client for ages. Now, whenever I start the client, it is downloading <code>block 135407</code> and does <strong>not</strong> progress past it.</p>

<p>What can I do?</p>
 10084: <p>I had a similar problem, but the <strong><em>-rescan</em></strong> option didn’t help.</p>

<p>In my case, there were a lot of lines referring to orphan blocks in my <em>debug.log</em> file (not 100 % sure it’s related but it may):</p>

<pre><code>2014-08-18 20:52:57 ProcessBlock: ORPHAN BLOCK 0, prev=00000000000000001132f6ac32387e51960e3154b2ad4420bdeb64d77999388f
2014-08-18 20:54:00 ProcessBlock: ORPHAN BLOCK 1, prev=00000000000000000e9926124cabed78be0ae8bab22fb20acc643e94749120f8
2014-08-18 20:56:37 ProcessBlock: ORPHAN BLOCK 2, prev=00000000000000001b3f790fc107051c17702d305b08a3ae6325f40ecf44eae9
...
</code></pre>

<p>Finally, I tried to restart the client with the <strong><em>-reindex</em></strong> option which fixed my problem (but took 100 % of my CPU usage for several hours while reprocessing the blockchain).</p>

<p>So if the rescan option don’t work, don’t give up, try the reindex option!</p>
 1087: <p>Okay, based on the comments I have tried a couple of things but in the end only the following worked:</p>

<ol>
<li>Close Bitcoin client</li>
<li>Backup files from %APPDATA%\Bitcoin</li>
<li>Optional:Download Block chains from:     <a href="http://sourceforge.net/projects/bitcoin/files/Bitcoin/blockchain/" rel="nofollow">http://sourceforge.net/projects/bitcoin/files/Bitcoin/blockchain/</a> to prevent lengthy initial download <strong>(Warning: the link advises against doing this if you have transactions in your wallet).</strong></li>
<li>Start Bitcoin client with the
<code>-rescan</code> option from command line. </li>
</ol>

<p>After that the client started downloading blockchains again. This worked for me. Not sure if this will work for everyone.</p>
 3668: <p>I had this happen to me once. It was apparently caused by an incompatible peer node. </p>

<ol>
<li>Delete <code>$HOME/.bitcoin/peers.dat</code></li>
<li>Restart <code>bitcoind</code></li>
</ol>

<p>Afterwards, new compatible peers will be found, and hopefully, you'll start processing blocks as expected again.</p>
