Rockbox iBasso DX90 totally busted

[cholero]

I've tried to create a playlist from the computer for my DX50 for the first time. Therefore I've used foobar2000 with wine on Xubuntu.

Default paths:
M:\checkout\Prodigy, The - The Day Is My Enemy\02 Nasty.ogg -> did not work

Then I did some tiral and error:
checkout\Prodigy, The - The Day Is My Enemy\02 Nasty.ogg  -> did not work
checkout/Prodigy, The - The Day Is My Enemy/02 Nasty.ogg -> did not work
external_sd\checkout\Prodigy, The - The Day Is My Enemy\02 Nasty.ogg  -> did not work
\mnt\external_sd\checkout\Prodigy, The - The Day Is My Enemy\02 Nasty.ogg -> WORKED 
/mnt/external_sd/checkout\Prodigy, The - The Day Is My Enemy\02 Nasty.ogg -> WORKED 
/mnt/external_sd/checkout/Prodigy, The - The Day Is My Enemy/02 Nasty.ogg -> WORKED    (as expected)

I only expected the last line to work. That means that I don't have an explanation why your  playlist do not work. Maybe the Text-Editor that you've used to edit the playlist saves the file in ISO8559-1 coding instead of UTF8?