Tried today replacing it with 8x 4gb model hynix 4gb 2xR4 pc2-5300f-555-11.
Are you actually referring to 2x 4R or 4x 2R? Note that the 2950 server does not support Quad Rank memory modules. If the memory is supported, then they may be faulty. Try with 2 memory sticks at a time on Slots 1 &2. The server supports up to 64 GB of memory