I love gigastudio but had a hell of a time working out why after I installed it, my system would automatically reboot at random times. It turns out that with Gigastudio 3, they have coded a driver called FILESPY.SYS into the application that scans your files on startup, and causes instability on your system. Even after I uninstalled gigastudio, it left this orphan file in the system32\drivers folder, which kept crashing and freezing my machine periodically. As soon as I removed this file, all returned to normal.
I have posted numerous questions to tascam without a reply. I hope by me stating this that it helps others out there that may be experincing similar problems. I even did a crashdump analysis of around 15 minidumps with windbg and this was the culprit.
I came upon that dll by accident and didn't know it was exclusively a giga file. nonetheless, I deleted it. Can't say that's the only reason your system would reboot though. I've found that giga is much like a woman. She's not gonna tell you where her sweet spot is. You gotta find it and until you do, she'll just be faking it! I'm still looking.