Nokia :: E72 Signals Disabled Upon Connection With Web Browser

I'm new to this forum, and joined out of necessity as I have a strange problem which wasn't solved by servicing or replacing the phone.I have a new E72 and my old phone was (or I still use it) E51.

When I'm at home (!) my E72 shows full signal, "3G" symbol, etc., but when opening the web browser and trying to connect to inernet, the browser crashes immediately and can only download "0 kb". Also friends trying to call me have their calls directed to voicemail or "recipient unreachable". SMS messages do not necessarily arrive immeadiately, but only after I have booted the whole phone. Funny thing is that OUTSIDE my house this problem never seems to occur (OK, I don't know if someone tries to call me and doesn't reach, but seems like the web is working always). I live in a normal apartment building in the middle of Helsinki, the capital of Finland, so there should be no problem of signal and all the signal seems to be at full strength. I'm writing this message on my laptop using a 3G wireless connection - no problems.This was never happening with E51 (same SIM-card and operator) So, I took my E72 to service and got it back week later, or in fact I got a "new one" as they said. In fact, there were still some photos I took before taking the phone to service so perhaps it was the same phone anyway - but had just been reconfigured or something. Anyway - no change in anything. Doesn't work reliably at home. So my only guess is that is there some antenna / connection problem or whatever? Any ideas anyone?

Oh, by the way, I'm and engineer and relatively patient with electronic equipment and did test the phone all around the house and outside, in a train, at office, everywhere. The problems ONLY occur at home.