After a few minutes of gameplay, the buy menu stops working right. I can use every other part of the menu fine, but clicking in the right part of the buy menu, the part with the buy button and the list of things being bought, fails. Same thing happens with controllers. Thoughts? Anyone else have the same issue?

That kinda menu related stuff is always a mod. Just take them all out, reinstall and put them back in 1 at a time. If that doesn't work, then you're screwed.