Okey, i have my setup a bit different.

The Octa have the midi out to the Virus. Then midi through from the virus to my Analogue Solutions Europa Sequencer midi in, then midi out from the europa to my TR9090 drum synth. The Octa is setup to send transport, clock and program change.

The Virus is setup as SEQ (Press Multi and Single at the same time to enter SEQ mode) as i mentioned.
Pressing PART on the Virus will step to the different parts. Each part also have the corresponding midi channel assigned to it. For example, Part 2 is the same as midi channel 2 and so on…

So… on the Octa i then setup 8 midi channels (1-8) with a different sound for each part on the Virus.

This setup works really good for me, and i have no problems what so ever with either midi or the Virus. The Virus is running OS 5.1.6.0.5 (latest beta for osx).