Pretty sure the OP is not
actually cutting a CPU pin.
Link for X61 pinmod: http://thinkwiki.de/Mehr_Power_f%C3%BCr ... nkl_Tablet
It's whatever chip that generates clock signals. Cutting that pin raises FSB from 200MHz to 266MHz. As a result, your DDR2 667 RAM now runs at 886 MHz, and many RAM sticks don't take this overclocking very well.
To do this properly, you have to get a DDR2 800 RAM and flash the SPD chip so it thinks it's only DDR2 533. Then, it will run at 711MHz, which is below its original rating of 800MHz. All details are in the link above if you read German. On the other hand, since things seem to work out fine for you right now, just use it and accept the risk of memory corruption.
And no, please don't ask me how to do this because I know nothing about the procedure, except that people have done it before.