I wasn't sure whether to post this here or in H/A, but since it's a more technical problem I figured I'd get a better response here.
First, some background: I have an iPhone 3G, on T-Mobile Croatia. It's running 3.1.3, and isn't unlocked, jailbreaked (jailbroken?) or hacked in any way. Both USB and BT tethering were available to me from the day I got it. When I plug it in via USB and the drivers are present (via iTunes), the clock turns blue and says "Tethering", so that's functioning normally.
Lately I've been tethering it more and more, and I've noticed the tethering is extremely crappy on it. The speed is fine, once I get a download going I get decent speeds, and the Speedtest app is reporting decent numbers as well. The problem is the reliability of TCP / UDP connections: all too often a connection will time out, my browser will complain it can't get a DNS query resolved, or a page will load with half the pictures missing. Then I have to hit refresh a couple times and most of the elements on a given page will load. This has been happening for a long time, but since I wasn't tethering that much before I didn't notice it. This happens in all the browsers I've tried, basically in all network applications.
First I thought it was a problem with the reception on the phone, but browsing on the phone (in mobile Safari) is flawless. Also, I popped my SIM card into a 3g stick I have, and browsing over that is flawless too.
Then I thought there was a problem with the software on my computer, since my experience with iTunes has been less than stellar. I tried USB tethering on my home laptop, running XP and Ubuntu Lucid, my netbook running 7, and my fiancee's laptop running XP. Then I tried bluetooth on my XP partition. Basically none of that worked, with the same symptoms every time. Also I was pleasantly surprised at how simple tethering was to set up in Ubuntu.
Now I'm getting kinda stumped. As far as I can tell, it's the phone software that's fucking up the tethering, and there's not much I can do about it. As far as I can see, my options are:
1) Bug the drones at T-Mobile
2) Wait for iPhone OS 4.0, jailbreak it, try another tethering method
3) Install Android when David Wang gets the port done
Has anyone else encountered problems like these, and maybe done something about it? I'd appreciate any advice.