I guess the answer is how you define "bug?" To Grace Hopper it was a moth stuck in a relay. You describe an addressing error that sound hardware-like in origin such as a bad trace. If it recurs with Mech's RAM, then check your traces for any disrupted lines by using a multimeter. There is a program out there for checking which RAM socket, but I can't recall the name.
In the end there can be only one, Highlander! I meant to say in the end you only need a RAM buffer for data transfers on the card, and 512k is plenty. Use another source of RAM for the system if need be.
