Hi, fcntl() locks don't work over NFS, unfortunately (well, I'm told they "sort of" work in 2.2 kernels, but I wouldn't count on it). Even if they work over NFS they may not work with other networked file systems or on non-Linux systems.
So the fix is actually complicated, libPropList needs to use a different type of locking. You might want to ask the libPropList author about it. Havoc