CH - Looks like you have a bit or two of flaky RAM then.
First question : How much RAM have you got in there and how many "slabs". To expand :
When you open the "box" and look inside - how many memory "slabs / sticks / thingies" have you got ?
How much memory is there - it says this on startup.
Let's have the answer to that and I will get back to you ...
MG