Whoops i have the 310.... similar thing perhaps applies however. Besides you can prob pick up a 310 for £100 or so these days. That one lasts 2 whole marathons and more and with a USB charger you can extend that to cover several day long races too
When i had the same issue Garmin Tech Support point you towards making sure its fully upto date on the software then it sorts it self out usually.
As for tooth pain well it is a brely noticeable ache but it is also still taking a while to vanish which is kinda odd being you are generally meant to have sorted it out halfway thru antibiotics course as the other half is meant to kill off what little remains. I however can tell there is still something in there although it could be a tiny bit right on the nerve i guess.
Aye i have a second lot of amoxicillin not fully kicked in yet as this time it had reached swelling status. Last time the pain was gone by evening. Mind you less pain this time and what little i get now and then ibuprofen deals with well enough.