Version 52.1 w/Lightning, Google Task Sync and Provider for Google Calendar on Windows 7 64 bit - Every time I try to dismiss, I get an error about the alert having been dismissed on the server, but when I pick Submit anyway, the error box goes away but the alert doesn't clear. If I pick Reload, it immediately returns the error again. Also, sometimes it will sit there and alternate between "2 reminders" and "26 reminders" (depending on how many are built up at the time) and use up all of the CPU task slots available to Thunderbird, sometimes I have to shutdown T-bird, other times some magic combination of Closing dialog boxes, dismissing all, something will make it stop flashing.The Events and Tasks column on the right of the T-Bird display is also flickering with this flashing, and it flickers a couple/few times a second. The submit anyway button seems to work the best in this spot. Ping me if you need any specific info or tests - I will do what I can, although I don't have time to debug it for real.