This issue started occuring several hours into playing, before that it was working fine. Basically, I can equip two 1H weapons at a time, but when I try to equip 2 spells, one of three things happens:
1. I can only equip one spell at a time, and it's automatically equipped to the left-mouse, regardless of whether I tried to put it on left or right.
2. One spell is automatically stuck on my right mouse click, and if this is a destruction spell I can double it, or equip another spell along with it. However, I can not equip a weapon along with it.
3. Occasionally it lets me select two spells, but once I pick them (and this is through the magic interface, not the shortcut 'q' menu) I can't change them unless I restart skyrim.

And it should be noted that I have reinstalled twice, restarted my computer, checked if my specs are sufficient, checked firewall compatibility etc, none of this helped.
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Help would be appreciated. Thanks.