On some of our CAD-stations, the "edit toolbox component" menu item is only present once for a newly inserted toolbox part. If the part is edtied (e.g. a different size screw used), the next time you RMB the part, the menu no longer contains the "edit toolbox component" option.
It seems that this behaviour is not present on older WinXP-workstations, but on newer Win7. All stations run SW2012 SP2.
Could it be some setting? We checked the toolbox-settings, they seem to be identical.
I believe I have the solution check to see if for some reason under you add-ins that your sw toolbox browser and sw toolbox add-in is unchecked.
if it is unchecked recheck them and reopen your assembly you should have the ablity to edit your toolbox component now.