Cannot shutdown.Help needed urgently!!!!

[harpoon]

I have an AMD Athlon xp 2400+ processor, on an MSI chipset KM 400-8235,256 DDR RAM, with a 20 GB HDD.Just upto yesterday I could properly shutdown /restart my machine but now it refuses to do so.After clicking shutdown /restart the machine do not responds at all.
There were no changes except 1).Live updates were installed 2) Broadband connection was installed.I have also uninstalled Norton Antivirus & have gone through most of the steps available in Windows Help but to no use.
Please somebody help me with a concrete solution.
Regards,
Suman.[img] [/img]

[navjotjsingh]

What os are you using?
Also try this: before shutting down close all other programs manually.

If that does not help then:

Scan your pc for viruses, use Spybot, MS anitspyware and lavasoft ad-aware se to check and delete all spywares.

Post your hijackthis log file.

Update your Windows.