I've been having a weird issue when I try to switch the gain knob. The camera tells me Cannot Proceed. I'm not in any auto mode as far as I can tell. What's the deal?

I also left my camera to record a long take and instead of continuing recording onto the 2nd card, it just stopped! What's da deal, guys??

Your first problem sounds as if you have your Direct Menu setting set to "All". This disables the physical switches and only allows changes via the screen. To enable the physical switches, go to your OTHERS menu and scroll down to "Direct Menu" and change it to "Part" or "Off". You should then be able to change the gain using the switch.

I don't have any ideas about your second problem.