The Samsung drive's eject mechanism is near the front of the drive, and can become gunked up, producing the symptoms described above. Lubricating the tray and the head retraction mechanism solved this problem for me. I make no warranty that it will work for you.
HOWTO strip down a Samsung and lubricate the tray and head retraction mechanism:
Do not lubricate the area of the spindle that the rubber band runs in.
Do not touch, breathe on, or get oil on the laser lens. As much as possible, avoid contact with the laser assembly.
Remove the decorative tray front (the black plastic 'xbox' piece).
Unscrew the four screws on the bottom, and remove the metal covers.
Press the white tab on the front with a screwdriver until the laser unit moves down, and the tray moves forward.
Pull the tray out as far as it will go.
Press down on the two tray latches, and pull the tray forward, removing it from the drive.http://www.llamma.com/xbox/Repairs/Samsung...Disassembly.htm
has photos of the disassembly of a samsung drive. You need to disassemble the drive down to 'Removing the DVD tray, two clips need to be depressed on either side of the front of the DVD to allow its removal'
Disassembly (tray mechanism)
Remove the rubber band from the motor to the spindle.
Carefully, with a small screwdriver, compress the latch on the spindle hub, and remove the spindle.
Remove the gear the spindle connects to.
Compress the hub of the white swing-arm, and remove it. It has two latches, so this may require three hands.
With a q-tip and oil, lubricate the white slider. Make sure to get the entire length that it runs over, and the channel the peg on the laser assembly travels in.
Lubricate the three hubs the spindle, gear, and swing-arm rest on.
Lubricate the insides of the spindle, gear and swing-arm, where they attach to the hub.
Lubricate the channel in the arm of the swing-arm that the white slider travels in.
Lubricate the three channels in the bottom of the tray.
Slide the slider all the way to the left (as you'd look at the drive were it in an XBox). Replace the gear and spindle.
Slide the slider a little to the right, and replace the swing-arm
Slide the slider all the way to the left again, and replace the rubber band. Slide the tray back in until it clicks. Make sure the leftmost protruberance on the slider is correctly inside the channel on the bottom of the tray.
Replace the metal covers and screws.
Replace the decorative tray front.
Plug the drive in and power on - it should correctly retract the tray. Verify the tray opens and closes, and the drive can read CDs/DVDs.