[inquisitor]

I don't know what the cause is, but during a cruise in the Baltic Sea in August I had similar problems with simyo. Every now and then I couldn't establish data connections (sometimes for minutes, sometimes for hours), allthough it worked before and I did not change the network. Also my Nokia E71 didn't register on some networks, on which it was registered earlier. That happened in all countires, I used simyo (Denmark, Sweden, Estonia and Finland) and I tried it also ashore, so it was not caused by interferences on the high sea.
I think eplus has a quite unreliable data and roaming platform.
Since your phone has worked properly before, the branding can't be causal for your issues.