left click in MSAccess

when I open my access db in edit mod (keeping the Shift button pressed) I can
use the left click/context menu to perform some functions.
When I open the db directly (opening a main form through the autoexec
macro), the left click does not function (no conetxt menu comes up) at all,
altough I can perform the functions by using the functionalities on the main
taskbar.

??