I am not sure that memory is the issue. I was having problems keeping my castaway bot logged in for more than a day at a time. My solution was to replace the entire computer with another backup pc I had laying around. The two systems are almost identical as far as CPU and memory. Honestly, I have no idea why but the bot now is able to stay up without crashing no matter how long its connected.
I wish I kept the old system so I could compare them, but it went to the city dump the next day. One thing I do know is that both systems had three memory slots and each slot was filled with 3 - 512mb memory chips. What made one crash constantly and the other one stable I do not know.
EDIT: I used the video card from the old system in the new system.
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Never! Never! Never! take a sleeping pill and a laxative at the same time.