Your cura printer settings and start gcode section probably has some commands setting speeds for marlin printers. Check your start gcode and delete any such lines, and also choose reprap gcode flavor.
Well isn't that great. As soon as I made this post, I decided to redo all the sd card contents in a 16GB SanDisk drive instead of the 500Mb stock one. Refreshed the www folder with a new download from the latest github and it seems to be working again.
