Error building 64bit webapp

because I can’t use Feedback (it doesn’t work thru our proxy), I post my issue here:
I try to compile my webapp to 64 bit, but the “linking executable” doesn’t work:

C:\Program Files (x86)\Xojo\Xojo 2015r3.1\Xojo Resources\Win32\HoudiniAssistant64.exe: C:\Temp\xojo scratch\VIA 1-6-8.xojo_binary_project [2BA6777B]\Linux_x86_64\/Dlg_Dnderung_Fahrt.bc: error: Could not open input file: unknown error[/quote]

There are ca. 20 other issues where the description is only “1”