Unplug the system, remove the battery and hold the power button 30 sec.  Remove and reinstall the memory modules and try powering up.

A flashing num lock means a memory error.

If that doesn't solve the issue, try one module at a time in each socket until the problem ceases.  If one module causes the fault in both sockets, replace it.  If both modules fail in one socket, the socket is bad;  replace the system board.