Some of my latest experiences, please add your own or comments.
-Cubase pre-loads or checks all VST/VSTi on startup. If during this check a plugin fails, you'll get a popup. The faulty XTC dev. is named on lower right corner of Cubase's boot popup. In 85% of the cases, copying the .dev from c:SFPDevices c:SFPDevicesXTC solves the porblem. Autowah-wah I could not get to work, I renamed the .dll to .dllbak to disable the cooncerned plugin.
-In XTC project, I found 24bit ASIO drivers working best. 16 and 32/flt work too, 24 seems better, it loads in less attempts

-I can use XTCi (only in Green Direct mode), but no XTC inserts. I get tremendous crackles/disto when I do. Anyone knows how to solve it? How do I use the XTCdelay's?
-Anyone ever succesfully inserted XTC into a Rewire channel? Rewire doesn't compensate for latency and causes same crackles here. This problem returns each installation, while inserts on ie. audio tracks have worked once.