Infinity ward said

We’ve updated the PC version of Modern Warfare 2, including the following fixes:

- Care Package, Emergency Airdrop, and Sentry Gun marker grenades sprint speed normalized.
- Sentry Guns: Improved placement detection, preventing cases of Sentry Guns inside geometry.
- Model 1887: Bling using Akimbo and FMJ combination now has same range and damage as non-Bling Model 1887s.
- Improved player collision removing cases of getting into geometry and ‘elevators’.
- Mouse latency tweaks for more mouse movement consistency. (PC-ONLY)
- Fixes to prevent various texture (PC-ONLY) and XP hacks.

These fixes, excluding the ones I’ve labeled as (PC-ONLY), are currently in test for the Xbox 360 and PS3 versions as well. Before you ask why there is a delay from PC to consoles, it’s because we can update IW-NET directly and therefore the fastest. The console versions require additional testing through their respective manufacturers.