Modern Warfare 2 - IWnet_ Invalid Version Error

When you try to connect to IWnet then it gives error : IWnet_ Invalidversion.

Updating MW2 in Steam doesn't help.


Waiting on more information and possible fix.

Update :

Unknown WHY files got corrupted /set-back to older version. But....

47. Modern Warfare 2 - IWnet_ Invalid Version Error

Solution: Verify integrity of game cache. To do this open the steam menu, right click modern warfare 2 and click properties. Go to local and select verify integrity of game cache.

or

Un-install and Re-install MW2

Full list of ALL Call of Duty Modern Warfare 2 Errors - Freezes, Crashes and Install problems