I've had problems listening to songs on soundcloud on Xubuntu - but only on *some* computers: Clicking the "play" button just didn't do anything, whereas on another PC it worked
Even if the computers had the same OS-, and Flash-plugin-version...
[SOLUTION]
Thanks to a post by "sdavmor" on the Ubuntu mailing list, I found out that it wasn't a Linux/Flash issue, but a problem with the "NoScript" Firefox AddOn.
Soundcloud works fine with NoScript disabled (the whole plugin/addon).
I haven't yet played around with resetting/configuring the NoScript...