I may have the same problem with 4.8release, gnome desktop and 4 of my laptops/PCs I have tried it on.
I have not had time yet to examine any error messages or the official mailing lists, but will do tomorrow.
Also, check for an updated pkg in the ftp directory and as a workaround, I am using the gnome-mplayer package, it has much improved since 4.5 (yep, I've skipped a few releases on my main rig
)