Hello guys,
I'm experiencing the same issue here with my project. It is quite messy.
By the way
Bjoern Graf, your solution works, in fact, building from XACT first ( but only for release or debug , configuring paths manually since there is just one path per plateform ), then building from VS and killing the xactbld3.exe process, the files exist because XACT created them before, it can be deployed then without any problem through the Xbox.
Thanks. I'll go with that for the moment.