Title says it all - suddenly all hostile NPC stopped attacking. They just stand there in aggressive poses, red on radar and wait for me to shoot them down.
Is this ME2? What platform and specs? Where's it happening? What have you tried? Etc, etc. My advice is to repost in the tech support forum for the appropriate game and platform and read the stickied thread about the information you need to provide for one of the technically minded people to be able to help you.
Well, in case someone got it too: for me that was console activation. Small program (Mass Effect 2 PCC Patcher) that helps you to activate console has several additional options. One of them is "blind AI" - means enemies do not see you (and your companions do not act either). Though the option was unchecked, I guess it somehow stuck.
Reinstalling PCC Patcher with that particular option "off" solved the problem for me.