Weapon Mod Pickup Bug
This is the second time I've encountered this bug. I'm playing ME3 on the Xbox 360. I googled this and found it to be a known issue but I haven't found a solution for it.
The first time is on the Priority: Mars mission. I picked up the weapon mod SMG Lightweight Materials but the bottom-right screen didn't pop up letting me know what I just picked up. When I went to the workbench, which is right next to where you find the mod, the mod is nowhere to be found.
This second time, I'm on the Priority: Sur Kesh mission to save the female krogan for the genophage cure. After the alarm sounds off in the lab, I try to pick up what I think was an Assault Rifle Extended Barrel. Same thing: no bottom-right screen pop-up, no weapon mod.
This is my second playthrough of the game. It's weird because my first playthrough was extremely smooth, no bugs whatsoever.
I'd like to note that in both instances, I had also just downloaded some new DLC and also encountered the "Checking Downloadable Content" freeze bug at the Main Menu. The first time, I figured it was the DLC so I deleted it. That didn't work so I went so far as to re-format my HDD and start a new game. It didn't really work. Eventually I thought it was some very random configuration of my created character that was creating the bug. Since Priority: Mars was at the start of the game, I basically just kept creating characters with slightly different physical characteristics. Eventually it just worked and I could pick up and use SMG Lightweight Materials with no problem.
Now that it's happening again, I don't really have the patience to mess around with random stuff and hope I don't get the bug again.