We understand how frustrating it is to be unable to play the game with out crashing. However, we will try our best to get through the bottom of this.
Can you please post your dxdiag so we can exactly know what your set up is? Are you playing on a wired or wireless connection? Can you post a link with your speedtest.net? Also, have you already tried verifying your game cache to make sure Ghosts files are not corrupted?Verify Game Cache Files (GCF) - How To's - Knowledge Base - Steam Support.
Thank you for your cooperation!
Hmmm.. Check the minimum requirements of the game first.
Here's for Black Ops 2.
OS: Windows Vista (Service Pack 2) or Windows 7; (Windows XP not supported)
Processor: Intel Core2 Duo E8200 2.66 GHz or AMD Phenom X3 8750 2.4 GHz processor or better
Memory: 2GB for 32-bit OS or 4GB for 64-bit OS
Graphics: Nvidia GeForce 8800GT 512 MB or ATI Radeon HD 3870 512 MB or better
DirectX®: DirectX® 9.0c or later
Hard Drive: 16 GB free hard drive space
Sound: DirectX® 9.0c or later
Internet: Broadband connection and service required for Multiplayer Connectivity. Internet connection required for activation.