Confirming:
Numpad 1: Working 100%
Numpad 2: Working 100%
Numpad 3: Working 100%
Numpad 4 (freeze timer): Freezes timer, but also freezes camera.
I'm using Windows 7 Business, 64-bit; SB 2600K at a relatively low overclock, 16GB of DDR3-1600 9-9-9-24 2t, and it's installed to a HDD. Have gone through all troubleshooting steps, no luck.
Interestingly, there's been a change from the previous trainer in how it handles Numpad 2 (infinite ammo/no reload); previously it would display a very large number (over-filled by about 7 or so orders of magnitude) beside a full ammo display. Now it seems to lock to 5 bullets. Not a big deal, though it does change it from being able to reload and have the full magazine size worth of "critical reload success" bullets. Now, you get one or two if you press the fire button faster than the trainer sets it back to 5, if your gun can hold more than 5 shots.
I don't know if that's intended; it's not a major issue regardless, but I thought I'd inform you since it's something else that's changed.
The obvious big deal is the mission timer, that is SUPER handy. That and infinite health are the big two, imo.
Helpful stuff ends here.
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I use Infinite Health like I'd use rations and health packs, I just hit it if I'm getting low and then disable it again - which means my character does not carry rations or health packs, preferring C4 and a shock grenade or the like, haha.
Yeah, I know in the end it still amounts to invincibility, but I could, theoretically, be one-shotted by a high damage enemy if my health is low, since I limit myself to pressing "Numpad 1" only when I'm at 25% health. It adds a little excitement back into the game, since guns do get suuuuper OP as time goes on.
Good luck hunting down the "Frozen timer = frozen camera" bug, man, I hope it's easy on you.