Please make sure that your Internet Explorer is not working in offline mode. For checking, run Internet Explorer, click on the File menu (if there is no File menu press Alt on your keyboard), then make sure "Work offline" is not checked.
HackShield may not properly be loading because a file is being blocked or has been deleted. Please make sure that any anti-virus-program and/or firewall program have Combat arms listed as a safe or trusted source. You can try to temporarly disable them and see if Combat Arms will run.
You may need to manually update your HackShield. During this operation please disable your anti-virus-program and firewall or make sure that the game is listed as a safe or trusted source. Go into your Combat Arms Folder, open your HackShield Folder, and delete the Update folder (By default C:\Nexon\Combat Arms EU\HShield\Update). Then, run the HSUpdate.exe. Once this has completed, please restart your computer. If this doesn't help, try uninstalling and then installing Combat Arms again.