Adding Desing to an Xilins Platform Studio project

Hi,
I'm trying to add an existing project which successfully synthesized and 
simulated with ISE 8.2 and Modelsim to an XPS-project.
It's verilog / VHDL Mixed, with the top-module being verilog with vhdl 
and verilog submodules.
so I started using the import peripheral wizard, and it is recognizing 
my .prj file correctly.

However I get an error in the HDL Analyzing Step:
HDLCompilers:87 - "C:\.....\top_module.v" line 217 Could not find 
module/primitive 'sub_module'

"sub_module" is a vhdl-entity though.

An I can't see any message in the log file like "Compiling VHDL Moduel..."

Only verilog-messages are appearing. In the HDL Source File Path the 
VHDL-Files are recognized. Yes, I put the language-droplist to mixed.

any hints?

Timo