Adding onto what has been said here;
1. You need to add Crossfire to your Anti-Virus Program... And Firewall's Exception's list, Scroll to the second post of this thread to see a Mini-tutorial on doing this correctly; [SOLVED] Common Solutions to Cross Fire Errors - Page 2 - Z8Games
2. I heard you saying you are using AVAST, this is the program that has the most conflict with Crossfire, I highly suggest you completely uninstall Avast and get yourself a new program, Something like AVG or McAffe.
3. When closing any unneeded programs manually, you might miss a few, Please use a program such as SmartClose to disable any unneeded programs; SmartClose download and reviews from SnapFiles
Programs that cause disturbances include;
Xfire, MSN, Skype, FRAPs, And Many more.
4. If you have used a Hack or Xtrap Bypass in the Past, Or have any Injectors open, I highly suggest you uninstall them or refrain from using them to help “Cure” This error.
5. It is unlikely but still true that you may be having a Virus or other malicious files that are attacking your computer and hence your Crossfire Game as well. Please run a thorough Virus Scan on your computer and be sure to restart immediately afterward.
AVG AVG Free | Download Free Antivirus Software | USA
MBAM Malwarebytes' Anti-Malware: Malwarebytes
6. You may need to clean your computer down with a program such as CCleaner, and in addition perform a clean and complete reinstallation of Crossfire;
CCleaner Download CCleaner 3.04.1389 - FileHippo.com
Full Reinstallation [GAME ERRORS] GUIDE - Performing A Clean Installation Due To Errors - Z8Games
I hope this helps!