two plugins at the same time = chaos?

When I use one instance of my sequencer plugin in live, everything is fine. However when I create a new midi track and put another instance of my plugin on it, both instances start syncing to a way faster clock (i.e. they are off tempo) but also it seems like only one can sucessfully transmit midi data to another track (eben though they are both routed to different outputs).

Anyone else had this experience? I assume from past usage of Pluggo that it should be totally normal to have multiple instances of the same plugins running.

cheers,
Danjel