Engineer:Cannot equip slots 4 or 5

[Tegana]

Have been playing an Engineer for the past week, and have had no problem equipping turrets or ammo packs through this morning.

This afternoon, I could no longer select either slot. There are icons visible in the slots, when I go to my loadout screen the items are equipped, but I cannot select them via either the mouse scroll or the number keys. When I try to select with the number keys, i just get a "blat" noise.
I've tried swapping my tank mines and ammo packs and sometimes I can access my mines, but never my ammo packs via direct select or turret "b" deploy.

Puzzling....

Anyone else have this happen?