I can't shoot with any weapon with my HC Tank (grenade launchers, rocket launchers, raygun cannons, fusion cannons, plasma cannons/waves, flamethrowers, freezer cannons and gatlin cannons... so all weapons and fresh bought from the npc's)
Rifle/pistol Spies and APU's don't have the problem. All weapons/spells work fine. So I created a new character to check if my character is buggy. But as I was in the woc temple to push my stats and draw the dirty knife there was no hit and no damage visible... The fists with ALT+H also don't work

As we figured out on the test server it's a class related problem. With a Spy, APU/PPU and PE you can hit with the fists. I lomed my PE on HC and.... surprise... the cannons work fine...
EDIT: if you have points on psi use and psi in your psi pool bar you can shoot with the hc/mc weapons.
The PSI consumption is increased, again? With the last patch a resist/combat/support buff took ~130 PSI. Now it's raised to ~173?? That's a little bit to harsh I think. Now you can buff one player if you have more than 450 PSI and take a PSI booster and wait a few seconds to buff the next player. The new formula should affect not all spell classes in common. The PSI consumption of the PPU spells was OK before.