MacBook detects a 4GB DIMM as a 1GB DIMM? I upgraded the memory on my MacBook (unibody, Core 2 Duo 2GHz).

I followed the instructions here and bought a single 4GB DDR3-1066MHz SODIMM.   

After installing it, the MacBook only detects 1GB:

BANK 0/DIMM1:

Size:   1 GB
Type:   DDR3
Speed:  1067 MHz
Status: OK
Manufacturer:   0x80AD
Part Number:    0x484D54313132533641465236432D47372020
Serial Number:  0x102E0000


Did I interpret the specs wrong? Should I have gone with 2+2 instead?

This points in that direction: "two SO-DIMM slots support up to 4GB".

Anyone got any experience?
You have a late 2008 MacBook Unibody (aluminum) aka MacBook5,1?

Your second link is pointing to an article about a different model.

According to Apple your computer supports up to 4GB ram (total), but people are running successfully up to 8GB.

Reputable RAM vendor such as OWC offers 8GB kit for your MacBook, however you should upgrade your EFI (quote from OWC):


  How to you ensure your MacBook/MacBook Pro can address 8GB of RAM
  
  Check the Boot ROM Version in your System Profiler at this link:
  http://support.apple.com/kb/HT1237
  
  MacBook Pros with a Model ID of MacBookPro5,1 should have a Boot ROM Version of MBP51.007E.B05.
  
  MacBooks with a Model ID of MacBook5,1 should have a Boot ROM version of MB51.007D.B03
  
  Machines with other Model IDs are not affected and don't need an update.
  If your Boot ROM version does not match the numbers above, download the appropriate
  For MacBook Pros (MacBookPro5,1)
  MacBook Pro EFI Firmware Update 1.8 (Apple.com Download)
  For MacBooks (MacBook5,1)
  MacBook EFI Firmware Update 1.4 (Apple.com Download)
  Once you have ensured that the Boot ROM is the correct version,
  make sure your Operating System is updated to Mac OS X v10.6.6.
  You must be running Snow Leopard to address 8GB on these systems.


Once you upgrade your EFI, you should be fine.