GStudio always put my computer into headache so I decided to work around to get the best of Giga.
If someone would like to try :
Download and install Midi-Yoke and Midi-Ox from http://www.midiox.com/
Map your instruments in your Gig library (I blended my Giga AO instruments in 4 Gig files, Strings 500 Mgs, Brass 350 Mgs, Woodwinds 450 Mgs, Percussion 325 Mgs and mapped all my instruments to midi patches.)
In GigaStudio set Midi In port to MIDI Yoke NT: 1 and forget about GigaStudio.
In Midi-Ox set midi inputs to your midi card and Midi outputs to Midi Yoke NT: 2
In your sequencer. set midi inputs to Midi Yoke NT: 2 and Midi outputs to Midi Yoke NT: 1. Load a midi file and set each channel to a midi patch already set in the Gig file.
Open GsEdit and load your Gig file (I can open and load my 4 Gig files, mentioned above, within 5 minutes).
All my channels are wide opened and sound perfectly. In the Windows Task Manager the CPU Usage meter allways stands below 60 %.
With midi-ox you can easily manage key switching with the instruments loaded in Gsedit.