user6529: I've got some trouble using bitcoin-qt.
It stays on: "No block source available...  242 weeks behind."
And "Catching up ... Processed 0" etc...
Map port using UPnP is activated, and proxy disabled and I have 7 active connections to the Bitcoin network. I tried without firewall or antivirus, but nothing happened. I went into log file and I saw this:
send version message: version 70001, blocks=0, us=1**.***.**.***:8333, them=*.**.****.**:8333, peer=*.****.***.****:8333
socket recv error 10054
disconnecting node 124.1

Don't take attention to the "*".
For each send in the logfile there is a socket recv error...
Edit : 
I'm running 
bitcoin-qt v0.8.3-beta
OS - windows XP pro sp3
I tried to put it off / on -> nothing else
What can I do? Thank you for your help.

user5406: You could try to:

Download the blockchain as a file and import it
force your client to switch to other peers
have you tried turning it off and on again?
have you tried reinstalling it?
have you tried putting your computer into another network?

Otherwise more information about what you have tried would be helpful, and we could use a bit more information such as, which version of the client and what operating system you are using. :)
Edit:
Just googled your problem again and found a bug report from 2012 where a person had "socket recv error: 10054". Somebody suggested the following (Please read the whole thing before applying!):

Take a look at (folder is hidden):
C:\ProgramData\boost_interprocess\Select LastBootUpTime from Win32_OperatingSystem
This one contains 2 files, 1 which consists of 32 "random" characters and looks like a hash and a BitcoinURL file of size 0. The files are there sometimes after a hard crash.
Delete the whole C:\ProgramData\boost_interprocess folder, restart the client, remove the database logs from the datadir and everything will work again.
It's related to stale files after a crash, which seem to come from a used lib in the Bitcoin client (some of the Boost ones).

To which the thread starter replied that it solved his problem.
MacOS
According to a comment on a similar question by Neil Neyman the respective folder can be found on MacOS at ~/Library/Application Support/Bitcoin/
To show your library directory in finder, hold the alt key while viewing the "GO" menu in the top menubar.

user4241: I had this same problem and I found these two posts 1 2 very helpful. What ended up working for me was going to preferences > Network, and turning off the SOCKS proxy, and then restarting the program. After that the network started to synchronize. 

user18196: I was having this problem. I updated my client to the newest version (https://bitcoin.org/en/download) and it solved itself. I think the clients might stop communicating with other clients who don't update. Haven't read that anywhere or anything, just a guess. 

The problem has returned, but updating the client is still a good thing to do.

6529: <p>I've got some trouble using <code>bitcoin-qt</code>.</p>

<p>It stays on: <code>"No block source available...  242 weeks behind."</code>
And <code>"Catching up ... Processed 0"</code> etc...
Map port using UPnP is activated, and proxy disabled and I have 7 active connections to the Bitcoin network. I tried without firewall or antivirus, but nothing happened. I went into log file and I saw this:</p>

<pre><code>send version message: version 70001, blocks=0, us=1**.***.**.***:8333, them=*.**.****.**:8333, peer=*.****.***.****:8333
socket recv error 10054
disconnecting node 124.1
</code></pre>

<p>Don't take attention to the "*".
For each send in the logfile there is a socket recv error...</p>

<p>Edit : </p>

<p>I'm running </p>

<p>bitcoin-qt v0.8.3-beta<br>
OS - windows XP pro sp3<br>
I tried to put it off / on -> nothing else</p>

<p>What can I do? Thank you for your help.</p>
 5406: <p>You could try to:</p>
<ul>
<li>Download the blockchain as a file and import it</li>
<li>force your client to switch to other peers</li>
<li>have you tried turning it off and on again?</li>
<li>have you tried reinstalling it?</li>
<li>have you tried putting your computer into another network?</li>
</ul>
<p>Otherwise more information about what you have tried would be helpful, and we could use a bit more information such as, which version of the client and what operating system you are using. :)</p>
<p><strong>Edit:</strong>
Just googled your problem again and found a <a href="https://github.com/bitcoin/bitcoin/issues/956" rel="nofollow noreferrer">bug report</a> from 2012 where a person had &quot;socket recv error: 10054&quot;. Somebody suggested the following (Please read the whole thing before applying!):</p>
<blockquote>
<p>Take a look at (folder is hidden):</p>
<p>C:\ProgramData\boost_interprocess\Select LastBootUpTime from Win32_OperatingSystem</p>
<p>This one contains 2 files, 1 which consists of 32 &quot;random&quot; characters and looks like a hash and a BitcoinURL file of size 0. The files are there sometimes after a hard crash.</p>
<p>Delete the whole C:\ProgramData\boost_interprocess folder, restart the client, remove the database logs from the datadir and everything will work again.</p>
<p>It's related to stale files after a crash, which seem to come from a used lib in the Bitcoin client (some of the Boost ones).</p>
</blockquote>
<p>To which the thread starter replied that it solved his problem.</p>
<p><strong>MacOS</strong></p>
<p>According to a <a href="https://bitcoin.stackexchange.com/q/13074/5406">comment on a similar question by Neil Neyman</a> the respective folder can be found on MacOS at ~/Library/Application Support/Bitcoin/</p>
<p>To show your library directory in finder, hold the alt key while viewing the &quot;GO&quot; menu in the top menubar.</p>
 4241: <p>I had this same problem and I found these two posts <a href="https://bitcointalk.org/index.php?topic=233943.0" rel="nofollow">1</a> <a href="https://bitcointalk.org/index.php?topic=291570.msg3121362#msg3121362" rel="nofollow">2</a> very helpful. What ended up working for me was going to preferences > Network, and turning off the SOCKS proxy, and then restarting the program. After that the network started to synchronize. </p>
 18196: <p>I was having this problem. I updated my client to the newest version (<a href="https://bitcoin.org/en/download" rel="nofollow">https://bitcoin.org/en/download</a>) and it solved itself. I think the clients might stop communicating with other clients who don't update. Haven't read that anywhere or anything, just a guess. </p>

<hr>

<p>The problem has returned, but updating the client is still a good thing to do.</p>
