I am having a similar if not identical problem. I upgraded using the link to 2.0 software. Everything worked great except it seemed I couldn't connect to the internet through wifi. Turns out I can connect, but the touch is painfully slow and it's hit or miss whether or not the page will download or wether I get a "server not responding" error. I've done everything I can find short of rolling back to 1.1.4 firmware (mainly because I don't know how). Here's some of the details:
1. All other computers/devices connect fine
2. I can see and connect to the wireless network, but transfering data is PAINFULLY slow.
3. I have upgraded to the most recent router firmware.
4. I got no errors during the update process.
5. I have restored several times, one of which downloaded the official apple 2.0 software and installed that. I have the same problem.
6. I have gone into the general settings and reset the network and "all".
7. I have performed a hard reset of the ipod touch.
8. Other internet apps besides safari have the same issue. ie. facebook/myspace apps.
9. the battery seems to drain much quicker as I mess around with this stuff... I'm assuming that has to do with the workout the wireless antenna is getting.
Anybody got any ideas?