I believe it's the same issue I reported in the previous thread. Not sure if davidlow7 is facing the same issue, since he complained about connectivity as well.

For me, the H, H+, 3G, E logo will suddenly disappear and I lose the data connection.

I found that Anand of anandtech also faced the same problems. I doubt it's the network. Someone suggested switching modem/baseband. I'm thinking of doing that but haven't gotten around to doing it yet. Too much to learn and not enough time to learn how to do it yet. lol. Rooting, flashing, cwm, titanium, etc etc etc. 

Edit: I'm using stock + upgrade to KH2 via Kies. This happens before and after I upgraded.

I have no power saving apps, but have the default power saving function ticked. It has no options to kill data connection, though, and my batt was at 80%, way too high above the threshold and I wasn't idle, but busy downloading.

Since me, aiman and Anand are on different carriers, i doubt it's the network.