Compiling question...

How comes my project compiles and run fine in debug.... but when I switch to release, I get linking errors?

CGraphics.obj : error LNK2001: unresolved external symbol _Direct3DCreate8@4
Main.obj : error LNK2001: unresolved external symbol _D3DXMatrixPerspectiveFovLH@20
Main.obj : error LNK2001: unresolved external symbol _D3DXMatrixLookAtLH@16
 

Looks pretty weird to me...