Do you guys know what to do if I am in a wifi area and I am connected, but instead of showing the red bars my reception bars are still there? Also, sometimes I am connected to a wifi area and it'll even say T-Mobile - "Router Name", but my wifi icon is still opaque.

I thought the red bars only showed up when you were in uma/UMA. As for when it says "T-Mobile - SSID" and your wifi icon is still opaque, I believe that's because you're not actually logged in to that network, but the phone "sees" it. That happens to me at school, I actually have to launch the browser and login with my school ID before the wifi is available for use.

When the wifi symbold is "opaque" it means that you don't have a connection to the Blackberry data system.

many times you need to try logging into a webpage for authentication first. Then it will allow your full connection.

I'm experiencing quite a similar problem with my 8120.

First of all: I have NO data plan. But I should still be able to just browse via WiFi in my home or university network, shouldn't I?

My WiFi symbol is always grey and I haven't ever noticed it turning black. The Name of the SSID does show though. When I am on the WiFi-Browser the icon is grey aswell and when I try to open a website it just says "Requesting.." and after some time it pops up the error message "Unable to connect to the Internet, please try again later.".

Here I gotta admit that it might be a problem with my home network. My Pearl says that it received an IP address, but it's not pingable and on my router setup page there is no device listed with that IP.
In my university network, the 8120 is pingable though, but I still cannot browse the Internet.

On my home network I tried using WiFi with and without encryption without any noticeable difference.
The university network has no encryption, but mac filtering enabled. My mac address is registered and as the BlackBerry is pingable, it should be at least properly connected to the network. The problem on my university network might be the proxy server.

Long story short, it might just be a problem with the WiFi networks I am trying to use. But I don't know what could be wrong with my home network.

Could anyone give my advise on or maybe even a solution for my problem?

Alright, I got the problem solved. I just updated my OS with the latest OS from this thread. Now I can use my WiFi at home to browse the Internet.