Notes Column in Project Tasks is Grayed out.

I am using SharePoint server 2010.

I have created a 'Project Tasks' page. I can see the Gnatt chart the default set of columns.

I would like to add a column where people can add notes or text related to that task. I added the 'Notes' column by doing the following - 

List --> List Settings --> Columns --> Create Column.

I chose 'Multiple Lines of text' from column type.

I can now see the column in my Project Tasks page. But when i go to edit it, it is greyed out. Wont let me write any text to it.

Any idea why this is happening?