I came to this forum looking to find an answer to a fatal startup error I get using GPO Studio. A few other users seem to have had this too:
It looked at though GPO was unable to load it's current ASIO driver, or choosing the "wrong" one. I had a browse through my registry (quite safe if you change nothing!) using a search for "ASIO". The DirectX ASIO driver was first in the list, so I located it (it was installed by a copy of Cubsae) and renamed the dll to filename.dlx (or whatever). The next time GPO loads it ignores that ASIO setting and loads the next, so loaded OK. You can then choose the device you wish to use.Portaudio error (-9997): Invalid sample rate (ASIO DirectX driver) - Unable to initialise audio driver
No installing or reinstalling of anything required!
You can even put back the offending ASIO DLL, but beware that the device list seems to be "dumb" in that is chooses a certain "slot" in the list, so adding a device back in will change the list contents, and therefore may change the selected device on the next load.
Hope this is of help to somebody.