Do you have time shift settings enabled?
Reason for asking is I had time shift setting enabled and was set to come on automatically after 2 mins, I was using a small(ish) memory stick and I found that it quickly filled up and caused me the very same problem.
I disabled the startup after 2 minutes so that I need to press pause to enabled it, deleted the EPG and downloaded it again. I've never had the problem since.
Hopefully this can help you some.