Hello herbgreen420
VirtualBox should release your mouse cursor without Guest Additions. Even with Guest Additions, this functionality may be required during boot before Guest Additions is started.
It may be that VirtualBox is not configured for right Ctrl or does not recognise it. Either way you can start the VirtualBox management window (not a virtual machine) and use File->Preferences->Input and use the "Auto Capture Keyboard" to re-set the Host Key.
You may not want to install the latest version of VirtualBox. It has recently gone from version 2.x to 3.x, now at 3.0.2. The last 2.x is more mature and stable than 3.0.2. The latest version is only the best choice if you need/want its new features.
Best
Charles