Exporting to YouTube format crashes Toon Boom Studio 6.0
Export to QuickTime from Toon Boom Studio and simply upload the clip to your YouTube account manually through your browser.
The best compression settings to use when you export would be: H.264
(in essence, all the export to YouTube does is render a .mov then upload it for you to your account).
Mac OS X (all)
Toon Boom Studio 6