STB question - odd

[alero_ecotec]

I had my struts/springs replaced about a month ago, and an alignment. I figured to save them the trouble I would take my strut tower brace off ahead of time, so it's been in my trunk untill today. I go to put it back on, pop the hood, start taking out the 2 nuts, 1 screw that are on the towers. However, one of the nuts won't come off, it just spins and spins. But it's not like the nut is just stripped or not threaded correctly. The threads and everything are spinning. I jacked the car up, but couldn't see anything from the underside to grab on to to keep it from spinning, so i'm kind of stuck at this point. Any ideas as to what's going on?

Strut mounts are bad. The bolts are attached on the front strut mounts-if they are spinning gotta replace them.