Is memtest always accurate?

[rosemarycane]

My T43 has been locking up on me intermittently. When I called the company from whom I purchased it, they suggested taking out the extra stick of ram they added to see if that would help. Just some background story, I purchased the computer from Thinkpad World online. They added an extra stick of 512mb when they received the computer from IBM. It is a reburb with a "L" classification.

Anyway, tested the memory with memtest and let it run for two cycles. Tests came back fine. Is it possible for the test to be wrong? I have taking the extra stick out anyway to see if this helps. Are thinkpads sensitive to the type of memory you can use. The stick I took out was simpletech.

I have a box coming from IBM either Monday or Tuesday so they look at the machine, but I thought if I could diagnose the problem myself, I would not be without a computer.