Your card may be minimal, but you have already played through at least once without this problem. So I gotta ask, "What's changed?"
Based on the symptoms, I'd guess a video driver...
I have the same issue. I'm on my fourth playthrough of ME3, and it's only started doing it now. I know it's not my card, since every other game works fine. I briefly saw a DirectX error one time so I feel like it's something to do with that.
I first thought I'd fried my card, but I no longer thing that since nothing else is gitching. I might try uninstalling and reinstalling, since the problem seemed to happen when I reintstalled Portal 2. I hope this gets fixed. I can't get past the last bit of the Leviathan DLC now.
Same problem, same DLC module. In ME2, particulary w/ the content pinned to Nos Astra/ Liara/ ShadowBroker, I learned that sweeping the player view and keying the space-bar sometimes accessed the reticule or released the sticking point, the method of exiting the game and re-entering play also works (mostly). In ME3, DLC- Leviathan .I had a stick-point; could not descend a ladder. Sweeping all the way to the "top" and keying to descend, I was able to break the stick-point, however, the interaction reticule requires constant efforts throughout the game in repositioning/sweep to acess. Disabling all 3d tech in the monitor has mostly solved the main in-game issues, but not for the Leviathan module. =(
