I'm having this same issue. All ports are forwarded in the firewall and windows firewall is turned off.
I have run C&C Online as administrator, and I'm patched to the latest version.
Here's my log:
----- C&C:Online Launcher Start -----
Game: Red Alert 3
Red Alert 3 Install Path: D:\RedAlert3\
Started game with: "RA3.exe "
Caught CREATE_PROCESS_DEBUG_EVENT from Red Alert 3. Detaching...
Found game.dat process. PID 100796100992101032
*** Starting CA public key patching routine ***
CA public key is expected value.
Successfully patched CA public key.
*** Starting hostname hooking routine ***
Injecting DLL into game.dat process...
Result of injection: Code -1073741582
Any ideas?