System slow down upon upgrade to 13.04

[marco07]

Hello Folks:
Last Friday I upgraded from 12.10 to 13.04. The upgrade went smooth without any glitches. I rebooted and started trying out the stuff. All has been OK until yesterday, when i noted some slowing down of the system. Again today i am experiencing a significant system slow down. Although everything works all right, there is quite a noticable delay in loading of applications and response to mouse clicks.
Also, since upgrading to 13.04, there has never been any update available at all through Muon package manager.
What went wrong? Please advise.
Thanks!

[marco07]

Well, no solution yet. It appears that perhaps I am the only one dealing with such an issue. There were a few updates available last night including one for kernel 3.8.??. It somewhat helped, but still quite slow relative to the speed I used to have with 12.10. BTW, I also noted that the screen saver not working either though it is properly set up in the system settings.
I will waite for next set of updates to see what happens. I hate to go thru a reinstall.
Any help will be appreciated.
P.S. The slowness does not seem to be caused by "Destop Effects" settings.
Thanks!

[Rog131]

Thoughts

Are there high CPU/GPU load ?

...the screen saver not working...

Are there error message when trying to start the screen saver ?

Starting from the console:

qdbus org.freedesktop.ScreenSaver /ScreenSaver SetActive 1

Or is the .xsession-errors big or has lot of errors when starting the screen saver.

[marco07]

Are there high CPU/GPU load ?

No. Not at all.

Are there error message when trying to start the screen saver ?

None whatsoever.

Starting from the console:

qdbus org.freedesktop.ScreenSaver /ScreenSaver SetActive 1

This command starts the blank screen just fine.

Or is the .xsession-errors big or has lot of errors when starting the screen saver.

No error message at all.
From system settings>Display and Monitor, when I test any screen saver, it starts well after rather a noticable pause. However, the screen saver would not start by it self upon the passage of pre-set minutes.

Overall, I feel after the latest update there is some improvements in the system performance, except the Firefox which is quite slow.
Any other ideas? Thanks for your help!

Edited Later:
I take my response to CPU usage back. The response was for an instance right after system start-up without any application started or running. Now I am noticing that after using Firefox and surfing the web, when I shut down the FF, the CPU usage goes up to 100% and stays there all the time. Then under a "top" command in konsul, I see a few instances of gnome-mplayer are shown to be still running, whereas the system is idle. I tried to kill each instance to no avail. Had to reboot the system to get back to normal. This seems to be the culprit and I cannot understand why after shuting down the FF, there are at least 4 instances of gnome-mplayer still actively utilizing 100% of CPU.