It is possible that the application preferences include values that are not compatible with the current configuration, or have been corrupted following a crash or power failure. This may also happen after installing system updates or plugging/unplugging displays.
To restore the default preferences, launch HighDesign holding the Command (Cmd on european keyboards) and Shift keys down. Please note: this will reset all the application preferences, such as startup options, autosave time, language, size and position of windows, etc.
The drawing may have been imported from a DXF/DWG file or some objects have been damaged. Use the command Help > Repair Document to try to fix the misbehaving items.
Sometimes, using the selection rectangle on seemingly empty areas can select damaged objects, typically imported from another format. Once selected, use the Delete command (Edit > Delete, or Delete/Canc key) to remove them from the project.
HighDesign is probably looking for missing resources, such as symbol libraries, or a recent document located on an external volume not currently mounted. You can mount the volume before launching HighDesign, or reset the list of recent items via File > Recent Items > Clear Menu.
If the delay is not caused by a recent file on an external volume, try resetting the application preferences: launch HighDesign holding down the Command and Shift keys.