R514 - Context 64 Bit available w. WinLeft+right Mouse only

[HeiWoMa]

Hi,
I run Windows7 64 Bit.
After start FC (514) the 64 Bit-Context is available. But after a while it is not available anymore I get the Default-Context. I can't find out when/why it happens. But with Win-Left+right Mousekey it is available shown. So there must be something that FC looses the Info that it runs on 64-Bit-Windows.