USB hub stopped working

After recent system update my keyboard and mouse connected via USB hub stopped working, although flash drive and external HDD were still recognized perfectly.

Thunderbird: how to open links in firefox (or other app)

There is one simple solution to set the right application for handling links in thunderbird. However finding the solution wasn't as easy, so here it is:
 

In TB 5.0 the hyper-links in the messages don’t work, even with the changes like these they do NOT work:
1) To be absolutely sure: make back up using MozBackup http://www.mozbackup.nl/
2) In Thunderbird, go to Preferences / Advanced /Config Editor (it will warn you, say yes)
3) Scroll down to network.protocol-handler.warn-external.http and make sure it’s set to true
4) Do the same for network.protocol-handler.warn-external.https
5) Do the same for network.protocol-handler.warn-external.ftp
6) Do the same for network.protocol-handler.external-default
7) Exit Thunderbird
8) Restart Thunderbird. The first time you try clicking on a link (or sooner) it will ask you to confirm that you’re using an external handler. Say yes and check the “Always do this” checkbox.

Thanks to Charell.

EDIT:
Recently, with thunderbird 31, the above steps are not working.
To change associated application, edit the mimeTypes.rdf file, placed in thunderbird's default profile folder.

Example: in my case, I wanted to change http(s) associated files to be opened with firefox-aurora, instead of firefox, so I've executed:

sed -i.bak 's/\(firefox\)/\1-aurora/g' ~/.thunderbird/m3e8sg0w.default/mimeTypes.rdf

VirtualBox: unable to remove CD/DVD Image from "Virtual media manager"

If you're unable to remove ISO image in Virtual Media Manager, check all your snapshots if they had your image mounted when they were created. If so, you need to remove them. After that you can remove the ISO image from Media Manager.

Mouse pointer freezing periodically for short time

Recently I've switched from Nvidia proprietary drivers to Nouveau because of youtube videos playback issues. The Nouveau driver runs smoothly, the GPU temperature dropped from 72° to 66° and youtube playback is smoother. Despite of this there was one small issue I've noticed. The mouse pointer was freezing for short, random periods about each 10 seconds.

KDE freezes for few seconds after login

This was happening to me for a while, with different KDE versions. KDE desktop is loading, almost before all startup programs are running but suddenly everything stopped. The plasma workspace freezed for 5-20 seconds. This was going on randomly, sometimes it has frozen, othertimes not.

File system check

To force fsck during next system start just run: sudo touch /forcefsck.

Note that using fastboot option in grub startup options disables fsck entirely.

Turn off Nepomuk and Akonadi in KDE4

If you don't need Nepomuk Semantic Desktop you can turn it off in System Settings > Desktop Search. After that you have to disable akonadi server to get rid of the error notification about problems with connecting to nepomuk.
This you can disable in:
~/.config/akonadi/akonadiserverrc
where you should change StartServer=true to StartServer=false.
Note that this change will disable KDEs KIM services such as KMail.