Thank you for contacting us. We are aware that a small number of new Apple MacBook and MacBook Pro notebook owners are experiencing issues when trying to install 4GB of system memory into their notebooks.
As we continue to track this issue, it does not appear to be isolated to any single brand of memory module or component or to a particular revision of either of these.
Crucial memory undergoes rigorous testing both at the module level and at the system level. Crucial memory is qualified on systems from most original equipment manufacturers (OEMs). This includes extensive testing specifically on Apple MacBooks and MacBook Pros to ensure that the Crucial memory upgrades you receive are not only of the highest OEM quality, but guaranteed compatible. Our parent company Micron is actually one of the original memory manufacturers that Apple uses.
We will continue to monitor this issue and of course offer you any support that you require. If you have any questions in the meantime, please don’t hesitate to contact us by visiting
http://www.crucial.com/support/help.aspx?tabid=sc3.
Please write your RMA number on the outside of your package and return the product to Crucial Technology within 10 business days.