I've just completed my angled house with diagonal objects. It looks awesome, but now my sims can't use most of the objects I've placed. I don't understand why it wouldn't work- as objects are objects, regardless of where you place them. I've used the following tools:

boolprop snapobjectstogrid true
boolprop allow45degreeangleofrotation true
moveobjects on

Has anyone figured out anyway around the problem?

not all objects can be used on diagonal, beds for instance. You just have to find what works and relocate the rest, I looked for a specific list for you but I couldnt find one at first glance, but I am sure there is one out there some where.