Display problems using 0.8.55 on Linux

Hi,

so, I broke my Calibre, I believe... I updated to 0.8.55 just now. After starting for the first time, the Calibre window was rendered on about 1/4 of my screen area, but the controls were at the same place they would've been had the window been fullscreen. This is kinda difficult to explain, for example, to get the preferences, I had to click on the desktop showing on the side of my Calibre window, and it actually opened the preferences (I could see which toolbar button was selected). I figured this might have something to do with the new display style, so I switched to the new style and restarted. This resulted in the window not being rendered at all. The window is there, I can see the tray icon and an active program, and when I click on the close program- button I get a dialog telling me that Calibre will continue running in the tray, but it's completely transparent.
I don't know where the Calibre config directory is, otherwise I'd like to at least switch off the modern interface style. Any other insights would be appreciated.

I'm running Calibre 0.8.55 on Linux Mint 13 64 bit. If any other data is needed, tell me.

Thanks in advance for any help!