This may or may not help, if you/your friend tries the OSX LW 5.3.0 beta version: LimeWire 5.3.0 (Beta) - Lime Wire

If your friend has an alternative hard disk drive or partition & enough space, could experiment by installing a second OSX system upon there to see if same problem occurs. eg: I was unable to use LW 5 for several months on my main OSX drive, but it did work on an alternative OSX installation on same computer. I think a reinstallation or OSX update eventually fixed my problem.

The Downloads.dat file is where your download history is stored. It keeps a record of your file download percentages.