[Help ASAP] Stuttering Problems with DirectX 9.0c

Problem Summary
Stuttering problems in some games, especially newer ones (presumably DirectX 9.0c games - older games seem to work fine - see below)

Problem Detail
When playing a game, the game is running really smooth and suddenly (randomly?) freezes for about 5 seconds, after which game continues to play smoothly with no problems, no errors, etc. Mouse will not work during this freeze. On some games, sound loops while frozen, on others sound disappears.

Problem Context

Currently it happens with the following games:

- World of Warcraft (latest patch)
- Madden 2006
- The Demo option found in 3DMark 2005 at the lower right corner of the menu

It does NOT happen in:
- Call of Duty United Offensive
- In the actual benchmark run by 3DMark 2005.


System Specifications

Athlon 64 3500+ Processor
Stock speed, heatsink and fan
MSI K8N Neo2 Platinum Motherboard
Generic 500W Power Supply
2 GB (2x1GB) Kingston ValueRAM Memory
Running at 400Mhz (PC3200), Dual Channel, stock timings (3-3-3-8); 1T setting (default is 2T)
20GB Western Digital IDE Hard Drive (7200 rpm)
120GB Hitachi IDE Hard Drive (7200 rpm)
BFG Geforce 6800GT AGP Graphics Adapter
Stock (comes pre-overclocked by BFG), running in AGP8x
Sound Blaster Audigy Platinum eX Sound Card
Comes with front I/O hub that connects to a secondary interface card
LG 40x/24x/40x (Write/Rewrite/Read) IDE Optical Drive
Lite-On 16x DVD+-RW IDE Optical Drive
USB 2.0 devices
8 ports, 4 used (2 Logitech Cordless Rumblepad controllers, 1 Microsoft Wheel Optical Mouse, 1 HP PSC 750 Printer)
Windows XP Professional
With Service Pack 2

Drivers
- Latest Forceware driver (v77.77) from NVidia. This driver is WHQL approved.
- Latest Sound Blaster driver from Creative. This driver is WHQL approved. All sound drivers were automatically installed from the Auto Update application in Creative's website.
- Latest NForce drivers.
- Latest BIOS (v1.9)
- Latest auto-updates/fixes from Microsoft

BIOS Configuration

a) Video settings
- Fastwrites disabled (tried enabled too)
- Sideband addressing enabled (tried disabled too)
- AGP Aperture Size 256 MB (tried 64 MB and 128 MB too)
- AGP 3.0 Speed 4x8x (tried Auto too)
- Video BIOS cacheable disabled
- AGP spread disabled

b) Voltages/Frequencies
- Everything set to auto
- Memory timings set to manual, keeping stock timings and setting the 2T to 1T. These settings are correctly entered, triple-checked them both with Everest and comparing to the 'Auto' setting. Also, have tried 2T.

c) Temperature
- CPU seems to be running at around 48°-59° C which is acceptable as far as I know.
- Video card is below threshold (below 110° C at all times)
- Fans running at full speed

d) MSI settings
- Cool'n'Quiet disabled (this setting was apparently causing my system to lockup at boot when I first installed Windows XP Professional)
- Dynamic Overclocking Technology (D.O.T) disabled

e) Other settings
- ACPI enabled
- APIC enabled from start (before installing Windows XP Professional)


My diagnostic
I am 90% sure it has something to do with the sound card, especially because on 3DMark 2005 the benchmark that shows the gunfight in a space base (soldiers hiding behind crates while being shot at, big guy blasting the enemies with a mega weapon, etc.) does not stutter or freeze at all and it runs without sound (since it is a video benchmark) but when I try the 'Demo' option, which features exactly the same sequence with sound, it froze two times (exactly in the same fashion described - i.e. it is NOT a hard lockup but a temporary, 5 second freeze).

Also my guess is that it seems to be happening with DirectX 9.0c software (this is just a guess since from what I recall Call of Duty United Offensive is DirectX9.0b and it runs fine - played over 10 hours without a single stutter).

Attempts to fix the problem
- Updated all drivers to latest version (see above)
- Changed settings in BIOS (see above)
- Lowered sound acceleration to 'Basic' in DXDIAG
- Tried using the built-in sound chip in the Motherboard (Realtek AC'97 7.1 surround sound chipset)
- Tried EAX3.0, then EAX2.0, then EAX and finally Miles Fast sound setting in games
- Tried different video resolutions
- Tried wiping temporary directories
- Tried shutting down all background processes
- Ran Prime95 Torture Test for 6 hours without a problem
- Ran Memtest86 for 6 hours without a problem
- Tried setting the video configuration to 'Performance' instead of 'Quality'
- Tried enabling and disabling antialiasing and anisotropic filtering
- Tried enabling Tripple Buffering
- Tried enabling and disabling VSync
- Tried disabling McAfee Antivirus Professional while running the game
- There is no adware or virus in my computer (fresh reinstall)

Other notes
- Only happens in some games (i.e., not on the desktop or while listening to music for example)
- Seems to happen at random (i.e., not at a certain spot/situation in the game)
- Tried to contact EA Tech Support, who failed to give a solution to the problem (suggested lowering sound acceleration, cleaning temporary files and shutting down background applications)
- On World of Warcraft while monitoring FPS, it is running smoothly at 60 FPS and when it freezes, after the freeze the FPS meter reads something around 3 FPS for half a second and then returns to the usual 30 FPS.
- Sound card is installed in PCI slot 3/5 to avoid possible conflict with the AGP bus.


Please help ASAP, I'm going nuts with this problem!
Please read the full post before replying - 95% of the time I get a suggestion I have already tried.
I can be contacted at ICQ (21979633), Hotmail/Messenger ([email protected]), Yahoo Messenger (biyectivo) and AOL (biyectivo).
Thanks in advance.