Hey, I tried opsu! again recently and I'm still getting the same error:
Mon Feb 02 21:24:03 PST 2015 ERROR:Unable to determine Slick build number
Wed Feb 11 00:40:29 PST 2015 ERROR:Unable to determine Slick build number
^That was in the .opsu.log file.
BUT I noticed that I can actually use opsu!, I just can't see it. I can scroll to change the volume, I can click to go somewhere (not sure where but it worked), I could use the "back" button after I entered whatever I entered and I even managed to guess where the Exit button was to close opsu! (I had to guess because my cursor disappeared when hovering over it).
Anyway, here's screen shot of how it looks (or rather, doesn't look):
I'll try other .jars tomorrow to see if it's just my own thing
EDIT: Oh yeah, and I can hear the music too