Can a extremely dirty cabin air filter prevent heat inside the cabin?

yes....plugged...yes will plug up the air flow~ https://www.google.com/#q=pontiac+grand+prix+cabin+air+filter+replacemen t&tbm=shop

http://www.youtube.com/watch?v=bmmn4ON_t0c

http://www.youtube.com/watch?v=dcL_0TWeZJY

Very unlikely. You will always get some recirculation air, even if you replace the filter with a block of wood. If it happened suddenly, it's a mechanical failure of some kind. First check your heater hoses to see if they are getting warm. If not, you may have a blockage, or a collapsed hose, or the t-stat is hanging open. If one hose is warm and other is not, the heater core control valve that sets the inside temp is probably bad, or you may have a clogged heater core although you would notice that getting worse over time, not suddenly.

Try topping off your coolant and bleeding the air out of the cooling system. That's what the issue was with mine

always check the easiest first. Was this a sudden event or a gradual thing? Do you have a temperature gauge that is reliable? Do you see any drops on the floor or road where it sat? Note where the water pump is located, if pump is going they leak. If thermostat is hanging wide open like mine was this fall you will notice the car not running well.... fast idle and running rich besides the fact that your freezing. Has the cooling system ever been introduced to STOP LEAK? That can and often does clog the heater core. Side note .... When radiator leaks replace it, its so much easier than the easiest heater core replacement. Some cars use vacuum to operate the temperature control valve. with proper amount of antifreeze and system bled correctly..... Im betting the heater control valve , follow the heater hoses.... Good Luck Btw Dorian was your car a Honda? They are pretty picky about bleeding. Two or three bubbles and no heat

Acting like a clogged heater core, upper coolant line - hot, lower - much cooler. Just replaced the cabin filter (yes, is was clogged), coolant is at normal level, and temp gauge movement and engine temp is normal. Also, attempted to bleed out any air from system, which was minimum, at best. Need to flush out the core. Thanks to all for their input...

If you have easy access to the hoses you can try this "last resort": connect your garden hose to a hot water faucet or spigot and flush the heater core, alternating between the two hoses. Run the water for no more than 30 seconds each hose. It's a pain in the ass, but try it for about 10 minutes. If the clog is due to corrosion, you won't see any improvement and replacement is the only option. If the clog is just oil/dirt/additive, you might be okay. It's worth a shot, and works about 25% of the time.