I do not know the answer, but I have the same problem and attempts to remedy by removing credentials, killing all processes, and re-entering (a solution posted in a number of other places) does not work. I have used Windows since 1992 and Ubuntu since 7.10, I am no expert but this looks like a real bug for Win 8 users. As U1 is my primary storage for files, I am forced to use a Win 7 machine to mirror U1 to SkyDrive and then access the files in SkyDrive on my Win 8 Toshiba Satellite C55. I know this is not an answer, but I suspect there is no answer at the user level. Uninstalling and reinstalling yields the same "please wait message."
Solved, for me, at least for now. Not a recommended solution for the faint of heart and carries the risk that an incorrect deletion may leave your system unstable. After an uninstall and killing all U1 processes in the task manager, I deleted all Ubuntu folders, all Ubuntu keys in regedit, credentials, everything I could find. I think some of the most important deletes that must be done as an admin are in the hidden folders
although that folder is now empty.
I then did a reinstall of UbuntuOne and it worked fine. My problem was that I had originally logged into an old account that I do not use and is empty. In trying to switch credentials to the correct account, U1 hung up on root match issues. Solving that led into the cannot sync morass.