Tonight's update to the HoloNet yields a LOT of additional information about Count Dooku. The following should be considered moderate spoiler material, so highlight to read at your peril!

SPOILER: Dooku was, confirming much speculation, indeed the master of Qui-Gon Jinn. Apparently it was Jinn's death that spurred Dooku (again referred to as the Count of Serenno) to leave the Jedi order. He disappeared 10 years prior to the time of AOTC, but showed up eight years later on various Mid and Inner Rim worlds "with a fiery rhetoric that has fueled the Separatist movement."

Click here to find out more about the man called Dooku... and thanks to AdmrlHunter for noting that this is the first official confirmation of this connection.