TL;DR Try unplugging your USB hub (and potentially other USB devices)
My Xorg did not consume a lot of CPU but within about a day that the computer was up, it bloated up to 1.2 Gigabytes of memory. The only way to correct this was a hard reboot.
After trying disabling NVidia drivers, switching to cinnamon, switching to gdm and finally kicking the damn thing (that was just for me to feel better), I noticed that as I switched to a console tty ( ALT + F1 or F2, ..., F6 ) during some gdm/lightdm service restart, there were a lot of error messages scrolling down the screen. Note, that I had only switched to ALT + F1, I had not logged in yet.
The messages were reporting that my usb tv-tuner card was not properly initialised. These messages kept scrolling on and on as if the system was stuck in an infinite loop trying continuously to initialise the tv card (and of course failing every time).
As expected, as soon as I disconnected the usb tv-card, the messages stopped, but to my amazement Xorg stopped inflating too. Just to make sure, I reconnected the usb tv tuner and the error messages came up, and again Xorg started gorging memory like an SUV filling up at a gas station.
But, right before the villagers (a.k.a ubuntu users) are about to smash their dysfunctional usb equipment and stone the dysfunctional usb equipment vendor, there is a sudden turn in the scenario. It is NOT actually the usb tv-card that caused all this trouble. The tv-card was only the symptom and not the source of the problem. The plot thickens...
Having used this tv-card before without an incident, I took a better look at the error message complaining about the tv-card. There was another line complaining about the usb port of the usb-hub, where I plugged in my tv-card. Hmmm, I had just bought this hub. So then I tried plugging the tv-card in a usb port directly on the motherboard. And everything worked fine! No error messages, and no Xorg bloating.
So at the end the actual problem was this:
Xorg was consuming memory because of initialisation errors of a usb device (and in my book this is a serious bug). Since a lot of people report problems with Xorg in ubuntu 12.04, I suggest that you also take a look at your usb devices. My tv-card could not be initialised when plugged in my new usb-hub, and that caused the problem. Putting it in a separate usb port on the motherboard fixed the problem.
P.S. The usb-hub is most likely either linux-incompatible, or should be replaced by one that has its own power adapter instead of being powered by the computer's usb bus (see USB hub not working properly Ubuntu 12.04). My web-cam also does not work when I plug it in the hub. It does work if plugged in a usb port on the motherboard. However note that, when I plug it in the usb-hub,
dmesg reports that the web cam is properly recognised and initialised (although
cheese gives me just a black image), and since there are no error messages, Xorg does not fill up the computer's memory.
P.P.S. I invite the distraught villagers to gather outside one-eyed Tim's barn, to throw their dysfunctional usb-hubs in a big festive bonfire. When the fire has built up, we will throw in the usb-hub vendor too. Free beer for everyone! Mua ha ha ha ha (deep voice laughter)
You can report bugs to Launchpad, but are these really bugs? Please can you tell us if you are new to Ubuntu, and then we can guide you further. From what you have said I would suggest you try to install the previous version of Ubuntu, 11.10, which is very stable indeed. But don't give up!
Update 8th May: I think everyone here will sympathise with you and your problems, but in defence of Ubuntu and the great bunch of guys working FREE to bring it to us, Ubuntu 12.04 is still a little guy, and so it is best not to jump the gun; as with the previous versions of Ubuntu, the team will try to iron out problems. I would strongly suggest that you go back to version 11.10 for a few months, and then upgrade when things have settled down more. Please don't desert Ubuntu, please support it for what it is.
Ok because no one else is willing to say anything. lm-sensors is the package in ubuntu that will help with your quest the first thing to find out is whether lm-sensors detects your gpu temperature sensor as this is what will probably control the speed of the GPU cooler fan. To test whether your gpu temp is detected you will need to paste this command in a terminal first.
This will go through a sensor detection script it will then output a section of code to add to your modules file which will load additional modules specific for your system. It should look some thing like this.
you will need to add this to etc/modules/ you can open it with
I suggest you take a look at the howto by DeMus on the Ubuntu forums as it goes in to much more detail you can check it here. lm-sensors howto
after you have got the output of the sensors command paste it at paste.ubuntu.com and add the link to original question and I will be able to see if you are going to be able to continue to the next level Quest!