Windows 7 holds on "shutting down"

When I shut down my computer, Windows gets hold on "shutting down" screen, forcing me to shut it off by pressing the on/off button.

I've tried disabling all services not related to windows on msconfig and all of the programs at start up, some times it didn't work though. Anyway that wasn't a real solution to me since I need most of those services to be running (bluetooth, ipod service, wlan, etc), same with programs.

Then I ran eventvwr (Microsoft Windows --> performance-diagnostics) and to my surprise there're over 932 event, with 132 being "critical" related mostly to Windows components (e.g: PNRPsvc) or essential drivers like "EHCI eUSB Miniport Driver".

Being the shut down issue the main problem, I've also been experiencing problems while the computer is either hibernating or suspended. When I wanted to resume Windows after any of those circumstances, sometimes it wouldn't, forcing me to shut it off "by hand" again.

Finally, at times it would give me a blue screen on startup ("STOP 0x0000007" related to:usbvideo.sys) and shut down. I haven't been getting it lately though.

My computer is a Dell Inspiron 14z, running Windows 7 Home Premium 64 bits. I got it last january and it's been giving me trouble for around 3-4 months now. I just can't figure out what's causing the problems.

Here are the events shown on the Event Viewer: http://cid-7023726809f16fde.skydrive.live.com/browse.aspx/Events?uc=1&nl=1