I have found that for some reason exclamation marks work for me. It just so happened that the tracks I tried had both apostrophes and exclamation marks. Removing both worked for me, but tracks by Hadouken! will load and play perfectly.
I do find this strange. Has anyone tried using the 'alternative' apostrophe `, rather than '?
EDIT: Just decided to try it. The 'alternative' (I can't remember what it's called) works. It's the one located above the TAB button on keyboards (Might be universal, might not. If not, just copy it from my post). This is some good news, since the lack of apostrophes in songs was killing the pedant inside me.
EDIT2: I had a very strange moment a minute ago. The DX50 doesn't read é when it's played, it just shows a blank character (i.e. a space). However, I tried listening to a song where both the artist and track had this character. The player stopped playing it 5 seconds in, screen went dark for half a second, and it reverted to playing a song I was playing before. I went back into directory view, but this time, it would not read é from filenames/folders, but accepted them in the tags. Very strange. It shows that the DX50 can support these characters, but that there is a bug stopping access to them.
Edited by Hobgoblinpie - 9/8/13 at 5:03am