This is exactly happening to me since a couple days.
I've been complaining and looking around as well without any luck.

At least you know it isn't specific to your setup -- or mine for that matter.

On Thursday 20 October 2011 6:57:14 AM Jonathan Marten wrote:
> This has started happening over the last day or so.  Messages are
> being fetched from the POP3 server, but neither KMail nor
> akonadiconsole will display them.  Kmail simply hangs when trying to
> start, akonadiconsole (Browser tab/Mail model) displays the folder
> tree and the message subject/sender/date but hangs when a message is
> clicked.
> 
> Lots of messages are appearing in the stderr log (ever 30 seconds or
> so) as follows:
> 
> "/home/ws/trunk/inst/bin/akonadiconsole(10738)" Soprano:
> "org.freedesktop.DBus.Error.NoReply - Did not receive a
> reply. Possible causes include: the remote application did not send a
> reply, the message bus security policy blocked the reply, the reply
> timeout expired, or the network connection was broken."
> "/home/ws/trunk/inst/bin/akonadiconsole(10738)" Soprano: "Unsupported
> operation (2)": "Invalid model"
> "/home/ws/trunk/inst/bin/akonadiconsole(10738)" Soprano: "Unsupported
> operation (2)": "Invalid model"
> "/home/ws/trunk/inst/bin/akonadiconsole(10738)" Soprano: "Invalid
> iterator."  "/home/ws/trunk/inst/bin/akonadiconsole(10738)" Soprano:
> "org.freedesktop.DBus.Error.NoReply - Did not receive a
> reply. Possible causes include: the remote application did not send a
> reply, the message bus security policy blocked the reply, the reply
> timeout expired, or the network connection was broken."
> "/home/ws/trunk/inst/bin/akonadiconsole(10738)" Soprano: "Unsupported
> operation (2)": "Invalid model"
> 
> "/home/ws/trunk/inst/bin/systemsettings(10756)" Soprano:
> "org.freedesktop.DBus.Error.NoReply - Did not receive a
> reply. Possible causes include: the remote application did not send a
> reply, the message bus security policy blocked the reply, the reply
> timeout expired, or the network connection was broken."
> systemsettings(10756)/nepomuk (library)
> <unnamed>::GlobalModelContainer::init: Connecting to local socket
> "/tmp/ksocket-jjm/nepomuk-socket"
> "/home/ws/trunk/inst/bin/systemsettings(10756)" Soprano:
> "QLocalSocket::connectToServer: Invalid name"
> systemsettings(10756)/nepomuk (library)
> <unnamed>::GlobalModelContainer::init: Failed to connect to Nepomuk
> server via local socket "/tmp/ksocket-jjm/nepomuk-socket"
> 
> Nepomuk is enabled in systemsettings, but file and email indexing are
> turned off.  The nepomukserver, nepomukservicestub (nepomukstorage)
> and virtuoso-t processes appear to be running.  No such socket
> "/tmp/ksocket-jjm/nepomuk-socket" as quoted above, exists, but I'm not
> sure if this is relevant.
> 
> Have tried removing the existing Nepomuk database and restarting
> nepomukserver, Akonadi and KMail, with no luck.  Has anyone any
> further ideas or suggestions?
> 
> Regards,
> 
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