sounds like a zip is not installed right or making good contact. a bent leg that makes intermittent contact with the socket could be causing this.
A zip that is on its way out could also cause this,but i'm guessing a bad connection. Reseat the custom chips(ramsey,dmac,etc) also. bad connection in the socket could act up.
Generally different brands of ram should live together fine..
If you are mixing page mode(part # ends in 400) with static column ram(part # ends in 402) be sure the static column is first in the zip sockets.
Agree it is probably not seated well, but I have seen 3000's give issues when certain brands are mixed. This is going back almost 20 years and I don't remember the details. Try using 8 megs at a time and see if it's stable. Could run an intensive memory test over night to see if something comes up.
I think you would want Page Mode in the first socket and not Static, since you would want the all the zips to run in page mode.
