Just to add my own voice to the choir: we had this issue around March 9th, where Feedburner stats flatlined for ~3 days, but came back (with the missing data intact), and I've noticed it's kicked off again, from about the 19th. So clearly it's not been fixed yet... but certainly on some corners of the internet it's suggested that Feedburner isn't a priority, anyway. I've not found a good alternative yet, but I wanted to add that last time it happened, it did get fixed, with no loss of data...