Are you using the same ethernet cable between the powerline adapter and either the pc or laptop?
If so, the I would suspect that the ethernet adapter on the pc is not correctly configured for the intended network.
Make sure that only one ethernet adapter is enabled on the pc if there is more than one ethernet port. One built-in via the motherboard and a second via PCI-x slot, or USB perhaps. Be sure to connect to whichever ethernet port is enabled.
Use "ipconfig /all" from the laptop's configuration to set up the pc's configuration: i.e., default gateway, subnet mask, etc.. PC may just have a configuration typo or some leftover configuration mis-match.