NGSolve wont load

I have a clean (no previous install) install of Netgen (6.2.1712) on Win8.1, but when I run Netgen I get this error in the command window:

loading ngsolve library
cannot load ngsolve
error: couldn't load library "libngsolve.dll": invalid argument
[0x7FFB45CDB390] ANOMALY: meaningless REX prefix used

and NGsolve doesn't show up in the menu.

Can anyone help?

Hi twospoons,

Please try to install another version (e.g. 1711) from here and check if you still have the same problem:
ngsolve.org/files/windows/