This site sums it up pretty well. Nvidia users need not worry that it's only their cards. It's interesting that Vampire Bloodline is having the same problem and it's a half-life 2 engine; thus, further proving that it's a game problem.
I've collected the following points based on my own experience and the information collected from hundreds of forum posts on this problem.
- It occurs on both Intel and AMD CPUs of all speeds.
- It occurs on systems with 2+ GB of RAM although it appears to be worse for users with 512MB of RAM or less.
- It occurs on both ATI and NVIDIA video cards, including video cards with 256MB RAM.
- It occurs with multiple sound cards and chipsets, including the Sound Blaster Live!, Audigy, Audigy 2, NVIDIA SoundStorm, Turtle Beach Santa Cruz, Realtek, etc.
- It occurs regardless of in-game screen resolution.
- It occurs for both CD/DVD installations and installations downloaded via Steam.
- It occurs on all supported versions of Windows including Windows XP Service Pack 2.
- It occurs on all supported versions of ATI CATALYST and NVIDIA ForceWare drivers, including the CATALYST 4.12 and ForceWare 67.02 beta drivers that contain optimizations for Source engine games.
- There are reports that lowering in-game texture detail and/or sound quality helps. I had to set texture detail to low before I noticed an improvement. This is unacceptable considering my system specs.
- This issue is not the result of the in-game auto-save feature as many people suggest. While the auto-saving may cause stuttering, the stuttering also occurs many times between auto-save points.
- The stuttering occurs in the same spot every time but only once per the loading of that level. I have recorded a 10 second demo that illustrates this. When executing the demo multiple times, the stuttering occurs every time in exactly the same spot. However, if while the level is loaded, you go back to the location of a previous stutter, it no longer occurs.
- According to some, this problem has existed as far back as the Half-Life 2 demos that were shown at E3. Indeed, if you go back and watch some of the footage, you can hear the audio stuttering as new scenes are loaded.
- The stuttering occurs in Half-Life: Source which has significantly less resources to manage than Half-Life 2.
- Vampire: The Masquerade, which is based on Half-Life 2's Source engine is also reported to have the same stuttering issues.