Edit /etc/ppp/ip-up and add the following line at the end:
/sbin/ifconfig $PPP_IFACE mtu 1500You’ll see that new PPP connections now have a MTU of 1500 when using ifconfig.
It would appear that an MTU size of 1396 for PPP sessions will sometimes cause issues when using Windows 7’s RDP through the VPN, no matter what the display options are. Fixing the MTU to 1500 as explained above fixed the black screen glitch right away. The problem was on the server after all.