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I am facing these weird problems after updating Ubuntu 12.04 with apt-get update && apt-get upgrade:

  1. It takes too much time to come to the Plymouth theme after selecting Ubuntu from the grub menu. Is it possible to correct this?

  2. On the login screen, before entering the password, whenever I move the mouse, it is kind of lagging/stuck. Only after entering the password and pressing Enter, it works normally.

I think this may be because of the updated kernel.

If so, is it possible to downgrade the kernel to the previous one ? If that is not the reason, what can be the problem?

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@Mitch , what edits have you made ? – Roshan George Jun 2 '12 at 9:31
I changed the format. Click on where it says edited above the name, and it will show you exactly what was done. – Mitch Jun 2 '12 at 9:33
After a new install of 12.04 (Unity) and throwing the updates on my disk I have the same behavior at LightDM's login prompt. If I open one the menus in the upper right corner the stuttering stops, closing the menu by clicking on the screen, and the lag returns. Found a bug report here: ATI Radeon HD 3200 (780G) with open source driver on AMD 64-bit – user74777 Jul 3 '12 at 14:25
up vote 1 down vote accepted

apt-get upgrade does not normally upgrade the kernel - you need apt-get dist-upgrade to do that.

First, disable the boot splash/plymouth by editing /etc/default/grub and removing "quiet splash", changing this line to GRUB_CMDLINE_LINUX_DEFAULT="". This will better let you see any errors/warnings during the boot process.

In any case, it is simple enough to go back to the previous one and see if the problems go away -- at the grub selection menu, select "Previous Linux Versions" (screenshot 1) and then select the top entry (screenshot 2). Note that the exact kernel names may not be the same for you!

enter image description here

enter image description here

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Sorry to say that, I forgot to mention that I issued the command apt-get dist-upgrade, and I have the grub menu like the above given one. – Roshan George Jun 2 '12 at 12:11
i plan to go back to the 11.10, which i think is more stable. What is your opinion? – Roshan George Jun 3 '12 at 1:35

As for the Plymouth problems, simply boot into a previous Linux Kernel version using Grub2. To fix the mouse errors in the login screen, you will have to install Ubuntu Tweak to change the GTK theme in LightDM that is causing much of the lag.

sudo add-apt-repository ppa:tualatrix/ppa
sudo apt-get update
sudo apt-get install ubuntu-tweak

Open Ubuntu Tweak, go to Tweaks, Login Settings, Unlock, and choose 'Adwaita' as the GTK theme. Adwaita will probably need to be installed via the Software Center. Problem solved :)enter image description here

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