This is a known issue affecting both the 2014.3 and 2014.4 versions of Sysgen.
It occurs on both Windows and Linux OS.
A patch exists for Windows 2014.3 and is attached to this answer record.
Instructions are included in the patch_readme directory within the patch archive as well as below:
This library patch is compatible with Vivado 2014.3 only and is not required for Vivado 2014.4, however it is necessary to perform the rename step above in Vivado 2014.4 as well.
This issue can also occur on a Linux OS.
To work around this issue on Linux, you need to rename the same file as for windows.
However, it will be in a .so file format as opposed to a .dll.
If you encounter any issues, please contact Xilinx Technical Support for assistance.