I had recently bought MTS connection which gave a usb stick to connect it. It also gave a rpm for the GUI. Later I found that due to it, some software like vlc and skype had stopped working.

I used to get errors like this:

roshan@localhost:~/Downloads$ vlc
VLC media player 1.1.3 The Luggage (revision exported)
Blocked: call to unsetenv("DBUS_ACTIVATION_ADDRESS")
Blocked: call to unsetenv("DBUS_ACTIVATION_BUS_TYPE")
Warning: call to signal(13, 0x1)
[0x9e9c8fc] main libvlc: Running vlc with the default interface. Use 'cvlc' to use vlc without interface.
[0xa02ba9c] skins2 interface error: no suitable dialogs provider found (hint: compile the qt4 plugin, and make sure it is loaded properly)
[0xa02ba9c] skins2 interface error: cannot instanciate qt4 dialogs provider
[0x9e9c8fc] main libvlc error: interface "default" initialization failed

roshan@localhost:~/Downloads$ skype
Fatal: Cannot mix incompatible Qt libraries
Aborted (core dumped)

The problem was with the linking of Qt libraries.
roshan@localhost:~/Downloads$ ldd /usr/bin/skype |grep -i Qt
libQtDBus.so.4 => /usr/lib/libQtDBus.so.4 (0x00406000)
libQtGui.so.4 => /usr/local/bin/ztemtApp/bin/libQtGui.so.4 (0x00efa000)
libQtNetwork.so.4 => /usr/lib/libQtNetwork.so.4 (0x002eb000)
libQtCore.so.4 => /usr/local/bin/ztemtApp/bin/libQtCore.so.4 (0x0084e000)
libQtXml.so.4 => /usr/lib/libQtXml.so.4 (0x00122000)

The libraries installed by the MTS stick had screwed the system. Notice that libQtGui links to /usr/local/bin/ztemtApp/bin/libQtGui.so.4.

So since I had forgotten which rpm had installed it I simply moved /usr/local/bin/ztemtApp/ to some location not in my path and things were back to normal.

roshan@localhost:~/Downloads$ ldd /usr/bin/skype |grep -i Qt
libQtDBus.so.4 => /usr/lib/libQtDBus.so.4 (0x00e24000)
libQtGui.so.4 => /usr/lib/libQtGui.so.4 (0x00eff000)
libQtNetwork.so.4 => /usr/lib/libQtNetwork.so.4 (0x002eb000)
libQtCore.so.4 => /usr/lib/libQtCore.so.4 (0x073ae000)
libQtXml.so.4 => /usr/lib/libQtXml.so.4 (0x00d1a000)