cant play videos

[varan]

hi.
host: windows 8
guest: windows 7
problem:
when i open a video (flv,mp4,mkv) in the guest-system the vlc-player closes without a message.
(same problem with windows media plaer. (klite-pack is installed))
does someone know how to fix that?

[mpack]

Enable 2D acceleration and install Guest Additions. See user manual for details.

[varan]

already installed guest additions (with 3d acceleration) and activated both