@twol I reproduce this problem.
scenario: only one device connected (USB with SDCARD)

if I unmount the unit (yellow) and then try to mount with red button (use as HDD) I get BSOD

Code:
<  4453.060> Traceback (most recent call last):
<  4453.060>   File "/usr/lib/enigma2/python/Components/Console.py", line 37, in finishedCB
<  4453.061>   File "/usr/lib/enigma2/python/Plugins/SystemPlugins/ViX/MountManager.py", line 297, in add_fstab
<  4453.062>     self.device_uuid = 'UUID=' + result.split('UUID=')[1].split(' ')[0].replace('"', '')
<  4453.063> IndexError: list index out of range
<  4453.063> [ePyObject] (CallObject(<bound method EnigmaLogFatal.write of <bound method ConsoleItem.dataAvailCB of <bound method EnigmaLogDebug.write of <bound method CList.__call__ of <bound method eSlider.eSlider_setValue of <bound method ClockToText.changed of <bound method ClockToText.changed of <bound method VolumeText.changed of <bound method CList.__call__ of <bound method Label.changed of <bound method CList.__call__ of <bound method eLabel.eLabel_setText of <bound method CList.__call__ of <unbound method eLabel.eLabel_setText>>>>>>>>>>>>>>,(1,)) failed)