Windows 7: How to fix slow startup according to network search

After starting Windows 7, the system is setting up the network connection (blue circle on network sign). I bought my Dell computer 2 weeks ago. It was very fast until this weekend. Starting up takes 10-15 minutes. When the network is found everything works fine again.

During the network searching it is possible to access internet by Chrome. IE and Firefox are not working. Looking for activated services by services.msc is also not possible.

- I tried to fix this by enabling all the non-windows related services, but no changes.
- I uninstalled and reinstalled the driver of my network card, with no success.

I don't have any clue on solving this.

Can anybody please help me?

Have you tried flusing the dns cache?
I would also reset the modem and router if any are involved in the equation.

To clear the dns cache
go to start enter cmd in the search box and hit enter
in the window that then opens type:
ipconfig /flushdns
hit enter
type exit
hit enter again.

Thanks for the fast reaction, although flushing the dns gives no difference...

it would help if we knew exactly what piece of the network information was missing. ...

Is it possible that the next time it's stuck like that you could do the same steps except
ipconfig /all
instead of
ipconfig /flushdns

that should give you a dump of all the connection information currently available to the system.
Might help if we knew exactly what it was choking on.

It would also help if you filled in My System Specs.