Been getting some strange behaviour with shadows recently.
What happens is, when moving around outside the game will pause for around half a second (probably as it's loading ugrids).
When it's done this I can carry on for a few steps at which point I'll get a slight performance hit and movement will stutter slightly.
If I then look around I get the following shadow/pixel corruption:

http://img.photobucket.com/albums/v480/StickyMick/ScreenShot52_zpsaa0c61b2.jpg

http://img.photobucket.com/albums/v480/StickyMick/ScreenShot50_zps0a75f08f.jpg

If I press esc key to bring up the game menu and press esc again this clears it until the next ugrid load.

The only mods I'm running are:

Remove Ambient Interior Fog
and
Green Water Fix.

System specs modest:

ASUS A8V-Deluxe + AMD 64/x2 3800
1.5GB RAM (Should have been 2GB but a 512 stick went down a few months back)
ATI Sapphire Radion X1950 Pro/512Mb
SB Audigy 4 soundcard.

Yep, I know it's old, but it runs Skyrim at 1024x 768 with 2x AA; 2x AF; FXAA = on
Texture Quality = High
Radial Blur = Medium
Shadow Detail = Medium
Decal Quality = Medium
All distance sliders at max
at 45 - 50 fps indoor locations
25 - 35 fps outdoor locations.

Any ideas?

Thankees in advance.

First of all, what are your specs as well as mods running?

Second, I hope you are not changing the UGrids. If so, leave it at 5. I don't know what makes people think it makes the game better, but it is really a ticking time bomb if fiddled with.

Anyway, give us as much info you can so we can solve this issue

Thankees for the prompt reply.
All info is there (had problems with uploading the screenshots, so I guess you caught my post between the edits).

Not made any changes to the UGrids at all.

Ok, so from your specs I think you are asking a lot from Skyrim for your system IMHO. I hate to sound like this, but just because it runs doesn't automatically mean it runs fine. Temps may be getting too high, your loss in memory may be affecting it, etc. Try lowering settings, even turning off some like AF.

I may be wrong, so hopefully someone with a lot more insight catches wind of this and provides their input

I'll have a tweak around, see if anything makes any difference.
Most of the time it'll will go for ages without any problems, then the next session I'll get the problems.

Temps are fine: CPU temps at 50 - 60 while running the game GPU temps hover around 50 - 60.

Thanks.