I'm having the same issues as well internet and market are down but email and a few select other things seems to be syncing just fine. It all start between 10:30 and 11:00 Mountain time and my zip is 80020. The internet and everything come back to life though when I get on my homes wifi network so I'm wondering if its Sprint's network acting up.
Everything here started around 11:30CST in 78701. On EVO - both 3G and 4G produce same results: a sometimes-internet connection that fades out and is slow. Apps that need connecting the the internet don't work. The Andriod Market wasn't working for about an hour, but now it is on- just can't download anything.
Mine is not working right now. As of this reply post I'm on the phone with a Sprint Customer Service Rep and he's having me go through several steps to resolve the issue with my phone (HTC Hero) and so far I'm still having internet connectivity issues. I've told the Rep I'm speaking with about the postings on this forum but he doesn't seem to take what's posted on these forums seriously and doesn't seem interested in what's being said here about the internet issues that others are having in different parts of the country.
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