We just recently purchased a Brand New Mac pro and decided to upgrade the Ram from 1GB to 4GB. Upon installing and everything, the Mac showed only 2GB of ram installed.
Has this sort of issue happened to anyone?

Also I know I read it in one of these forums about memory issues with After Effects 7 causing slowing downs, crashes and error outputs etc. Does anyone has a link on the adjustments/workarounds? I know some settings has to be modified but I can't find the link.

Please help!!!

To start off.

Make sure you have the correct kind of ram for your machine and make sure you are installing it in pairs using the same size/manufacturer.

This might help.
http://manuals.info.apple.com/en/MacPro_MemoryDIMM_DIY.pdf

It's possible for the RAM to look like it's seated properly when it isn't - I've had RAM not show up that was almost all the way in.