This weekend I experienced interesting problem. I don't now what happened with D-Link DIR-100 but it turned it to DoS machine. It wasn't unusual amount of traffic on interface, D-Link DIR-100 just was sending auth requests on port 1723 but it almost completely turned off my pptp-server on RouterOS. CPU usage in this time was 0-5%. Hardware platform - x86 AMD Phenom with 4 core, 256MB of operative memory, 1 GB of HDD. It was to ease to DoS.
After reboot D-Link 100 became to work properly.
Almost forgot, ROS versions 4.13 and 5.0rc5 - with the same result.