Hi guys, I had the TNT bug where after I placed the first TNT item it wouldn't let me place any more - but I managed to fix it... I'll detail how I did it here and hopefully it will fix it for you too, but if it doesn't then don't be flaming me.

I'm using Rage with the 1st update patch, I was also playing the game with a trainer (for infinite ammo, yeah I'm a cheater ) and used this all throughout my gameplay right up until the TNT bug. When I picked up the TNT I noticed in my inventory window the TNT didn't have any item count on it - as if I only had 1 of it.

I solved the bug by doing the following:
1) I loaded a save game that was BEFORE I entered the Blue Line station,
2) I went into Subway Town and sold all my extra supplies and ammo (thanks to using the trainer I think I had over-filled my inventory) so I was down to the bare minimum I'd need for the mission (this time I used the trainer for infinite health, no reload, and easy kills but NOT infinite ammo, just to be safe)
3) Went and entered the Blue Line station but this time didn't bother shooting at the mutants as I ran to the TNT box (as they we running away from me at this point)
4) Picked up the TNT package, checked my inventory and there was the proof - there was a '4' in the TNT slot
5) Played as normal until I planted the first TNT package, held my breath and ran to the 2nd place to place it... and HEY PRESTO, I could plant more TNT

I hope this information helps you to continue playing Rage

Play legit without cheats or hacks I'm pretty sure you wouldn't have had a problem.
This game is so easy to beat "on nightmare" I can't see why anyone would want to use cheats to start with. lol