No Size Change
Playing in 4:3 resolutions like 1600x1200(useful for non-widescreen monitors and projectors) results in some menu screens displaying incorrectly: the left and right hand sides of the screen are clipped (as if "zoomed in" too far), so important information cannot be seen (like journal details and the map legend). Screens affected include: Map, Party Selection, Planet details, and Journal. Currently the only known fix is to use a 16:9 screen resolution when playing, like 1920x1080.
Your squad, enemies, and objects that can be interacted with become boxy black blobs. This is a known problem on newer AMD processors - as the game uses the 3DNow! instruction set which was dropped in 2010 starting with the FX series of processors. To fix change the viewmode to unlit.
If the whole screen is black except for the UI, then Shepard fell through the Normandy and the save is bugged. Only happens on the Normandy, in the Engineering part of the ship. Never save there.
Activate the console (instructions on how to enable the console further down) and type At BIOA_NOR00 Start_BIOA_NOR00_01 and press ↵ Enter. This will place you at the entrance to the Normandy and you will be able to save and load your game with no problems. If you fall through anywhere else in the game, pctweaks has a comprehensive list of all the "At string newArea" commands.
At BIOA_NOR00 Start_BIOA_NOR00_01
FOR /F "skip=2 tokens=2,*" %A IN ('REG QUERY "HKLM\SOFTWARE\bioware\mass effect" /v Path /reg:32') DO REG ADD "HKCU\SOFTWARE\Microsoft\Windows NT\CurrentVersion\AppCompatFlags\Layers" /v "%B"^\Binaries\MassEffect.exe /t REG_SZ /d RUNASINVOKER
If you receive this message, it may be fixed by running the .exe in compatibility mode for Windows XP Service Pack 2. Be sure to do this for the actual MassEffect.exe and not the launcher. The final folder tree will be \Mass Effect\Binaries\MassEffect.exe. The preceding folders will of course depend on how you installed the game (via Steam, via Origin etc.).
The resolution listbox in graphics options does have up/down arrows on the right side, which are easily overlooked, that allow you to choose higher resolutions like 1920x1080.
Improves stability on 64 bit systems with at least 3GB RAM by allowing the application to use more than 2GB RAM.