It is normal for that message to appear. The files are part of a different workflow, so they can't be part of the state change.
Standard part contains the common parts which have assosiated with several drawings.
bt if this error is normal then this message/error/warning generates a doubt for the users.
Can we hide this warning?
There is no way to remove the waring (that I know of) but you control the warnings settins per group or by user by double clicking on the user or group to modify. The last tab in the group properties dialog is "Warnings" and that is where you control the warnings per group. The second to last tab in the user properties dialog is "Warnings" and that is where you control the warnings per user (these are 2009 settings).
Hope that helps!