I'm not sure if this is still reproducable with Qt 5.3.0, but the upstream seems to point to the libxcb upstream bug which now has a fix. Another Qt bug linked to the upstream Qt bug report was also reported fixed in Qt 5.3.0.
** Package changed: qtdeclarative-opensource-src (Ubuntu) => libxcb (Ubuntu) -- You received this bug notification because you are a member of Desktop Packages, which is subscribed to libxcb in Ubuntu. https://bugs.launchpad.net/bugs/1179617 Title: qmlscene assert failure: qmlscene: ../../src/xcb_conn.c:180: write_vec: Assertion `!c->out.queue_len' failed. Status in Qt: Fix Released Status in “libxcb” package in Ubuntu: Incomplete Bug description: - Spontaneous crash without any apparent reason. - Except the web browser, no application was in use at the moment of the crash. Thanks fabio ProblemType: Bug DistroRelease: Ubuntu 13.10 Package: qmlscene 5.0.1-0ubuntu3 ProcVersionSignature: Ubuntu 3.9.0-1.5-generic 3.9.1 Uname: Linux 3.9.0-1-generic x86_64 ApportVersion: 2.10-0ubuntu3 Architecture: amd64 Date: Mon May 13 20:02:17 2013 EcryptfsInUse: Yes InstallationDate: Installed on 2012-10-12 (213 days ago) InstallationMedia: Ubuntu 12.04.1 LTS "Precise Pangolin" - Release amd64 (20121011) MarkForUpload: True SourcePackage: qtdeclarative-opensource-src UpgradeStatus: Upgraded to saucy on 2013-05-01 (11 days ago) To manage notifications about this bug go to: https://bugs.launchpad.net/qt/+bug/1179617/+subscriptions -- Mailing list: https://launchpad.net/~desktop-packages Post to : desktop-packages@lists.launchpad.net Unsubscribe : https://launchpad.net/~desktop-packages More help : https://help.launchpad.net/ListHelp