Early 2008 mbp Memory Upgrade Issue

So I have an early 2008 macbook pro, in which I was using 2x 1GB sticks of RAM. (2 GB total) I went to upgrade to 4GB by replacing the 1GB sticks with these.

When I installed both new 2GB sticks, I got the 3 beeps of death on startup, indicating a RAM issue. I was worried that I'd bought the wrong RAM, so I tried a series of combinations of the old RAM and the new. The result?

Both new 2GB sticks work fine if put into the lower of the two RAM slots and paired with one of the old 1GB in the other slot. But, any combination of installations that involves putting a new 2GB stick into the upper RAM slot results in the 3 beeps. The really weird thing is that upper slot will still accept a 1GB paired with a 2GB in the lower slot just fine. My system is currently showing 3GB. I just can't get it to accept a new 2GB stick in the upper RAM slot.

Does anyone have any idea why this would be the case? Thanks in advance...
Edit/Delete Message

Apple states your machine will only accept 4 GB, however, Mactracker says it will hold and utilize 6 GB. (Mactracker is usually correct.)

The only thing I can think of is the memory you purchased is not compatible although they are the correct modules for that machine. What I suggest is returning them and purchase instead from OWC (Other World Computing) or Crucial. May cost you a bit more for the modules but both sellers are reliable.

But that's the thing....

(a) I've read the same thing about upgrade capacity, and I'm only trying to run 4GB anyway.

AND

(b) Both new sticks work just fine when put into the lower RAM slot. And the upper RAM slot will still accept the old 1GB sticks, it just won't accept either of the new ones.


???

I guess the solution is probably still to just return and try another product, regardless. (Unless someone out there knows something?!)

Thanks for weighing in.

Yeah, sorry but I don't have any other suggestion other than to return the modules and try different ones. I've seen stranger things than that when it comes to memory modules. If newer ones give you the same problem, then we can assume it's a hardware problem with the machine.