So I'm using a Creative Zen Sleek Photo, Ubuntu Feiesty, Amarok 1.4.5, and have libmtp installed.

I used mtp-detect and that detects the device, but for some reason Amarok doesn't.

SUBSYSTEM!="usb_device", ACTION!="add", GOTO="libmtp_rules_end"

# Creative Zen VisionSpecial:Recentchanges
SYSFS{idVendor}=="041e", SYSFS{idProduct}=="411f", SYMLINK+="libmtp-%k", MODE="666"
# Creative Portable Media Center
SYSFS{idVendor}=="041e", SYSFS{idProduct}=="4123", SYMLINK+="libmtp-%k", MODE="666"
# Creative Zen Xtra (MTP mode)
SYSFS{idVendor}=="041e", SYSFS{idProduct}=="4128", SYMLINK+="libmtp-%k", MODE="666"
# Second generation Dell DJ
SYSFS{idVendor}=="041e", SYSFS{idProduct}=="412f", SYMLINK+="libmtp-%k", MODE="666"
# Creative Zen Micro (MTP mode)
SYSFS{idVendor}=="041e", SYSFS{idProduct}=="4130", SYMLINK+="libmtp-%k", MODE="666"
# Creative Zen Touch (MTP mode)
SYSFS{idVendor}=="041e", SYSFS{idProduct}=="4131", SYMLINK+="libmtp-%k", MODE="666"
# Dell Pocket DJ (MTP mode)
SYSFS{idVendor}=="041e", SYSFS{idProduct}=="4132", SYMLINK+="libmtp-%k", MODE="666"
# Creative Zen Sleek (MTP mode)
SYSFS{idVendor}=="041e", SYSFS{idProduct}=="4137", SYMLINK+="libmtp-%k", MODE="666"
# Creative Zen MicroPhoto
SYSFS{idVendor}=="041e", SYSFS{idProduct}=="413c", SYMLINK+="libmtp-%k", MODE="666"
# Creative Zen Sleek Photo
SYSFS{idVendor}=="041e", SYSFS{idProduct}=="413d", SYMLINK+="libmtp-%k", MODE="666"
# Creative Zen Vision:M
SYSFS{idVendor}=="041e", SYSFS{idProduct}=="413e", SYMLINK+="libmtp-%k", MODE="666"
# Creative Zen V Plus
SYSFS{idVendor}=="041e", SYSFS{idProduct}=="4152", SYMLINK+="libmtp-%k", MODE="666"
# Samsung:YH-820
SYSFS{idVendor}=="04e8", SYSFS{idProduct}=="502e", SYMLINK+="libmtp-%k", MODE="666"
# Samsung YH-925
SYSFS{idVendor}=="04e8", SYSFS{idProduct}=="502f", SYMLINK+="libmtp-%k", MODE="666"
# Samsung YP-T7J
SYSFS{idVendor}=="04e8", SYSFS{idProduct}=="5047", SYMLINK+="libmtp-%k", MODE="666"
# Samsung YH-999 Portable Media Center
SYSFS{idVendor}=="04e8", SYSFS{idProduct}=="5a0f", SYMLINK+="libmtp-%k", MODE="666"
# Intel Bandon Portable Media Center
SYSFS{idVendor}=="045e", SYSFS{idProduct}=="00c9", SYMLINK+="libmtp-%k", MODE="666"
# iRiver Portable Media Center
SYSFS{idVendor}=="1006", SYSFS{idProduct}=="4002", SYMLINK+="libmtp-%k", MODE="666"
# iRiver Portable Media Center
SYSFS{idVendor}=="1006", SYSFS{idProduct}=="4003", SYMLINK+="libmtp-%k", MODE="666"
# JVC Alneo XA-HD500
SYSFS{idVendor}=="04f1", SYSFS{idProduct}=="6105", SYMLINK+="libmtp-%k", MODE="666"
# Philipps HDD6320
SYSFS{idVendor}=="0471", SYSFS{idProduct}=="01eb", SYMLINK+="libmtp-%k", MODE="666"
# Philipps HDD6320 2
SYSFS{idVendor}=="0471", SYSFS{idProduct}=="014b", SYMLINK+="libmtp-%k", MODE="666"
# Philipps HDD1630/17
SYSFS{idVendor}=="0471", SYSFS{idProduct}=="014c", SYMLINK+="libmtp-%k", MODE="666"
# SanDisk Sansa c150
SYSFS{idVendor}=="0781", SYSFS{idProduct}=="7410", SYMLINK+="libmtp-%k", MODE="666"
# SanDisk Sansa e200
SYSFS{idVendor}=="0781", SYSFS{idProduct}=="7420", SYMLINK+="libmtp-%k", MODE="666"
# SanDisk Sansa e260
SYSFS{idVendor}=="0781", SYSFS{idProduct}=="7420", SYMLINK+="libmtp-%k", MODE="666"
# iRiver T10
SYSFS{idVendor}=="4102", SYSFS{idProduct}=="1113", SYMLINK+="libmtp-%k", MODE="666"
# iRiver T20 FM
SYSFS{idVendor}=="4102", SYSFS{idProduct}=="1114", SYMLINK+="libmtp-%k", MODE="666"
# iRiver U10
SYSFS{idVendor}=="4102", SYSFS{idProduct}=="1116", SYMLINK+="libmtp-%k", MODE="666"
# iRiver T10
SYSFS{idVendor}=="4102", SYSFS{idProduct}=="1117", SYMLINK+="libmtp-%k", MODE="666"
# iRiver T20
SYSFS{idVendor}=="4102", SYSFS{idProduct}=="1118", SYMLINK+="libmtp-%k", MODE="666"
# iRiver T30
SYSFS{idVendor}=="4102", SYSFS{idProduct}=="1119", SYMLINK+="libmtp-%k", MODE="666"
# iRiver H10
SYSFS{idVendor}=="4102", SYSFS{idProduct}=="2101", SYMLINK+="libmtp-%k", MODE="666"
# iRiver H10
SYSFS{idVendor}=="4102", SYSFS{idProduct}=="2102", SYMLINK+="libmtp-%k", MODE="666"
# Dell DJ Itty
SYSFS{idVendor}=="413c", SYSFS{idProduct}=="4500", SYMLINK+="libmtp-%k", MODE="666"
# Toshiba Gigabeat MEGF-40
SYSFS{idVendor}=="0930", SYSFS{idProduct}=="0009", SYMLINK+="libmtp-%k", MODE="666"
# Toshiba Gigabeat
SYSFS{idVendor}=="0930", SYSFS{idProduct}=="000c", SYMLINK+="libmtp-%k", MODE="666"

LABEL="libmtp_rules_end"

Are you running mtp-detect as root and amarok as a normal user? Could this be possible?
Then the solution would be to set up your system in the way that also a normal user can use libmtp and the mtp device.

Marcel