bad ram slots??

i am running a
motherboard=gigabyte ga-k8ns nforce 2
bus 200
amd sempron 2.8
socket 754

3x 256 sticks of ram
vidiogeforcefx5500
crative 64

i been runnign ok for 5 months then

about 2-3 weeks back my pc started to reboot by itself
then started getting the bsod with
page fault
pfn_list etcetc
i took my pc to bare min
checked it and still dioing it
check my minidumps and they was on about memory defect
read a few post on this forum and started checkign ram and ram slots

i got 3 ram slots
1-2-3
and 3 ram sticks
ok
when i put any of my 3 ram sticks in slot 1 it runs great all the time as soon as i put other ram in slot 2and 3 with stick in slot 1 as well it starts freezing ,bsod etcetc
i tested all ram in separate slots and eveytime i use slot 2-3 by them selfs i cannot get passed the first bit of screen at the moment i running my pc with 1 stick of ram in slot 1 put all my software hardware back on and still runnign ok
i wondering it cannot be my ran sticks?????
can i have bad ramslots????
i know little bit about pc but not the bios stuff and changing timming and knocking down memeory etc or could it be somethig esle whats making it do that???
any thoughts i would apprechate