You could just be unlucky and have a router that has issues with devices such as blackberries. This is a fairly old (4-5 years) router so although it may not seem like it, it could be your issue.
Try making sure WEP is enabled, not only is it obviously secure, but it could help with the connection.
Check channel settings, if it's at 6, try 11 or 3. Sometimes the channel can matter.
As well, if you've never done a firmware update to the device, get the latest firmware and load it to the router, sometimes even that makes a difference.
If none of these options work, then you need a newer wireless router, that's pretty much the solution.
I would also recommend for Wi-Fi browsing getting something like Opera Mini. And if you're on a data plan, for sure get a data use monitor because although the 8320 is Wi-Fi, some applications don't always support using it so you can end up burning through your monthly data.
Hope some of this was useful