I have this exact issue with my prs-350.
It was fully charged on Tuesday, worked fine on Wednesday, I did not use it on Thursday, and on Friday (today), the screen is blank, the amber light is flashing, and the computer does not see it when connected.
I was able to fully charge it again with an AC adapter - I got it to go to a steady red light by pressing the reset pinhole and plugging in the AC. The light turned off after about an hour. Tried a regular reset again; after I press the reset pinhole for 5 seconds and turn on the power, the amber light blinks but the screen never comes on. With no display, I can't do a factory reset either.
The up side is it is still under warranty and eligible for an exchange. I really want to erase the contents before sending it away, though I don't see how that's possible if the computer won't recognize it.
Any ideas/suggestions?
Thanks!