Eversince changing to OSX 10.8 when I open DTP, the Download Manager Window opens. Is there anyway to prevent this happening?
This is the normal behavior as long as there are queued downloads listed in that window. If the window is empty it will (should) not open on start, when it has been closed before.
Here with DEVONthink Pro Office 2.3.5 this has not changed due to OS10.8.