Possible Duplicate:
I have a hardware detection problem, what logs do I need to look into?

I am using Ubuntu's Network Manager to connect to a local wifi router. My problem is, that it often disconnects without any visible reason (router is on, internet connection seems to be working, wifi diodes are blinking). I mostly have to disable wifi from Network Manager, enable it again to get wifi connecting again.

Plus I am often experiencing Network Manager trying to connect to my wifi, trying several times but then giving up.

I even tried an external usb-wifi card, but with the very same results.

My question is:

How can I debug this? Which logs should I read to see what is really happening when all of these errors occur - so I can post them here and see how to proceed?