Does the CUV4X or P3V4X support ECC RAM?
 

Yes, the ASUS P3V4X supports until 4GB of ECC memory. The specifications about ASUS P3V4X aren't completed correct because it supports memory modules of 1GB so that you can upgrade it until 4GB not 2GB as described here. The operative system can manage 3GB because it needs to use some addresses for the hardware that's because I've been using 3 memory ECC modules of 1GB, total 3GB. The system works perfectly with Windows 7 Professional 32 bit and the latest BIOS upgrade 1006.004.