RELATED: This question has led me to ask this one.

I had to change our unnamed crappy ADSL router to a crappy Comtrend CT-5361 WiFi router, now every WiFi connection to the domain doesn't work correctly:

• Joining the domain is impossible (see related question)
• Logging into the domain takes ages
• Authentication usually fails

Question:

• How to debug this and pinpoint the exact problem? I have no enough knowledge on either WiFi networks or on Active Directory to know which connections are made at which stages nor how to check what's happening at the wireless level to compare what should happen to what is happening.

I'm looking for resources to learn what should be happening and tools to detect what is actually happening (I expect a sniffer should be enough, but if there are better, more specialized tools, that'd be great).