This error is related to the lack of admin rights, the game fails to register blowfish.dll. It could also be your anti-virus program blocking the game.
I made a fix for Tiberian Sun to solve this problem, but it also works on Red Alert 2. Try it out if you cannot get it working manually
http://downloads.cncnet.org/Games/TiberianSun/TiberianSunDllFix.exe
