Disappearing Ram and Sleep Issues macbook pro lion

Hello,

I have been having an issue with the RAM on my macbook pro unibody, late 2009 (model 5,5), since i upgraded from the original 2x2GB to 2x4GB acquired on the internet, from a certified supplier (the equivalent of OWC in Italy): Sometimes, the computer does not recognize one of the chips, showing only 4 gb mounted, other times it shows both chips, thus 8 GB...but it seems to do so randomly. The ram dissapears especially after a permission repair and a reboot, or a hard reboot.

This issue occurred one week after i recieved the Ram, and i have checked by switching the chips with the original ones, and it occurs with the latter, too, so i have excluded the possibility of defective ram. I have tested the banks, and the one in which the ram is not detected is always the lower one, never the top one (Bank 1, never bank 0).

Since the occurring of this issue, i have also had issues with the Sleep mode: sometimes, when i send my mac to sleep by shutting the lid, it will go to sleep, only to never wake up when i open the lid, forcing me to hard reset it. the status led, when i send it to sleep, starts pulsing normally, but when i open the lid it turns off, but the display doesn't turn on, and if i close the lid the status led stays on, and after some while the fans start running (occasionally).

this happens often, but sometimes it doesn't. here too, it seems to be on a random basis.

If i, however, send the mac to sleep through the apple menu and then close the lid and wake it with the power button, no issue occurs.

I have tried resetting SMC, PRAM, cleaning caches, Advanced Hardware Test from the DVD, but nothing.

for what concerns the RAM, i have tried with both the original and the compatible ram by inserting either only in slot 0 (the uppermost slot), in which case it always is detected, and only in slot 1 (the lowermost), in which case it is never detected and the computer emits the system beep (but i believe this could be normal - i am no technician).

Then, last week, the computer booted up showing 7.60 GB total ram, but only in one slot, and the strange thing was that it didn't recognize 8 Gb or 7.75, but 7.60.

this got me worrying, a bit.

Has anyone had the same issues? or, better, resolved the matter?

By the way, i am running OS 10.7.2