If it's memory related, test with memtest86, and if errors are shown, test each stick individually. Clean the contacts of any stick that shows errors, (or better, all of them) and the contacts of the sockets,
Mister old-polack; Quick question if I may - have you got a suggestion as to the best thing to use to clean the sticks and the socket contacts?
I use isopropyl alcohol, with Q-tips and Bounty paper towels. This will sound like an add for Bounty, but they have a rag content that binds them together like no other disposable toweling, and allows them to hold up even with much stronger chemicals, while remaining soft and scratch free. I used them exclusively when working with composite plastic molding, for cleanup with various solvents, and waxing of molds, because they held together and left less residue than any other media. (think shedding, and stray fibers)
I keep a roll on my desk, to this day, to clean electrical contacts and my glasses. I clean the glasses two or three times a day, with the same isopropyl alcohol, applied from a wet Bounty, then buff them with a dry Bounty. Never had a scratch yet. There really is no equivalent product available.
The card contacts are easy. The socket contacts get a bit tricky, but a twice folded bounty dampened (not wet) with the alcohol can be gently slid between the rows of contacts in the socket, cleaning both rows with each pass. Gently really means... gently. You want the alcohol to dissolve the grim, rather than the scrubbing action of the towels. The towels will absorb the dissolved grim during the process. Sometimes I use a vinyl eraser on the card contacts, if there's any real accumulation on the contacts, between passes with the alcohol and towels. One more time, these things are delicate, so always gentle, gentle, and more gentle.
Vinyl erasers can be found in office supply and art supply stores. They are designed to remove pencil marks completely, without damaging even delicate paper. As the eraser wears it does not crumble and leave a dusty residue like rubber, but rather rolls strings of vinyl material that absorbs the material being removed, and are easy to clean up. Anyone old enough to have done any drafting work with real pencils and drafting machines, or water color artists, will be familiar with these. I even had rechargeable, variable speed, electric erasers that used 1/4 inch round sticks of this material for extremely delicate work. Some rat stole them, and i haven't found replacements yet.