Mixxx don't show files (and dirs) into Browse library section

Hi, I've installed Mixxx 1.10 on my Gentoo box: so I tried to use it but when I try to select a file from browse section Mixxx don't show any file or directory in any link in the left tree box.

trying to run mixxx from terminal i receive:

Warning: [Main]: failed to resolve JACK name method
Warning: [Main]: Requested control does not exist: "[Samplers],show_samplers" . Creating it.
Warning: [Main]: Object::connect: No such slot QGroupBox::setProperty(const char*, const QVariant&) in src/skin/propertybinder.cpp:13
Warning: [Main]: Requested control does not exist: "[Vinylcontrol],show_vinylcontrol" . Creating it.
Warning: [Main]: Object::connect: No such slot QGroupBox::setProperty(const char*, const QVariant&) in src/skin/propertybinder.cpp:13
Warning: [Main]: Requested control does not exist: "[Microphone],show_microphone" . Creating it.
Warning: [Main]: Object::connect: No such slot QGroupBox::setProperty(const char*, const QVariant&) in src/skin/propertybinder.cpp:13
Warning: [Main]: QGLContext::makeCurrent(): Cannot make invalid context current.
Warning: [Main]: Requested control does not exist: "[Spinny1],show_spinny" . Creating it.
Warning: [Main]: Object::connect: No such slot QGroupBox::setProperty(const char*, const QVariant&) in src/skin/propertybinder.cpp:13
Warning: [Main]: Requested control does not exist: "[Spinny2],show_spinny" . Creating it.
Warning: [Main]: Object::connect: No such slot QGroupBox::setProperty(const char*, const QVariant&) in src/skin/propertybinder.cpp:13
Warning: [Main]: X Error: BadValue (integer parameter out of range for operation) 2
  Extension: 128 (Uknown extension)
  Minor opcode: 16 (Unknown request)
  Resource id: 0x20de

Moreover I scanned my library but mixxx puts all my songs in only one "dir": so in the left listbox (qlistwidget?) I have all songs in only one list.