I have a rather strange problem, the same issue while attempting to run the game under wine or under windows XP (no Steam).
Everything loads, and I can start creating a new character just fine. However, when I get to the 'classes' screen, I can't open the dropdowns. The default values appear, and clicking the 'down arrow' next to them depresses the button (as though it were open, like any other program) - but the dropdowns don't actually become visible, and I can't select any option.
Another odd thing, if I start a game using the default options (since I can't change them) - when planning a day, I can select my actions properly, but then setting the options for that action (eg, choosing what subject to study) has a similar problem - nothing appears when I try to edit. However, in this case, if I minimize Academagia and then re-open, the pop-up will have shown up, and I can select what adventure to go on normally.
The previous version of Academagia ran fine under XP (but was a bit prone to crashing randomly), and not at all under wine. So one step forward, two steps back. ><;; I can provide screenshots and the log when I get home, if that will help, but wanted to explain the problem in case anyone has an easy suggestion to try.