I had pretty much retired Giga; I use Kontakt for pretty much everything and have converted all of my giga libraries to Kontakt format, but since I still have Giga and GVI on my slave, I thought maybe it would be nice to use them for the giga libraries like Sonic Implant Symphonic Strings.
So I fired up VSTack first and loaded GVI. It worked fine, was stable, but the first thing I noticed is it doesn't support program channel changes. Did they ever fix that issue in GVI? GVI is kind of useless to me without that. So I thought about creating ketswitched instruments, but to do that, I would have to do it in Giga 3. One other thing about GVI is it has an icon with GigPulse but it is not enabled. Can you use Giga 3's GigaPulse in VSTack with GVI or do you have to have the standalone version of GigaPulse?
So I booted up Giga 3. For some reason, I can now only load 1 instrument into Giga. If I try to load a 2nd instrument, it says there was an unknown system error. Can't figure that one out as last time I booted up Giga 3 (which was quite a while ago), it worked just fine. I have the 3.1 update which I believe was the last one released. Correct? I am going to try it again and make sure that absolutely everything is turned off besides Giga. (It is a P4, 3.0 Ghz with 3 Gb RAM and XP Pro so I never had any resource problems running Giga 3 in the past.) In the hour or so I played around with it, I got the blue screen of death 3 times; something I haven't seen in a while and something that has never happened with Kontakt.
So I am about ready to say screw it with Giga and just delete it from my system. Kind of sad really.
Not sure about your system error, but that message usually indicates that you need to tweak your RAM in the Giga system settings (do this from the configuration manager in Start|Tascam|Gigastudio...without Giga running. Run the test, pick a setting, reboot, try it. There are lots of old threads here about RAM management in GS3.
The latest update is 3.21. Works great for me. Should still be on Tascam's site.
You can only use Gigapulse in GVI when a preset is encoded to an instrument, and unfortunately, in GVI the gigapulse can only use single-source placements, and routing is not terribly flexible as in GS3. See this thread for discussion on encoding: