Check the clock battery. If it is leaking, the acid can corrode the motherboard beyond repair. Chip-RAM errors (green screen) can be caused by corroded conductors.
Also check the RAM socket. Could be a contact problem between the socket and the motherboard rather than between the RAM module and the socket.
Also try one of your Fast-RAM modules in the Chip-RAM socket. In the worst case a 4 MB module is recognised as 1 MB, but 1 MB is better than nothing. And if it works reliably with one of the Fast-RAM modules, you can find another 2 MB module as replacement for the faulty Chip-RAM.
Bye,
Thomas
