The connection is working fine (browser, email etc.) but I always get this error when trying to install something:

Resolving host timed out: downloads.maemo.nokia.com

I can install apps with the GPRS connection but I'd like to get my N900 working with the WLAN. And there are no problems with my PC.

well, I still do not know where is the problem, but the DNS is included in it.
There are times that goes well, sometimes simply do not connect.
Exist a Google software called namebench and found the best DNS for my network.
And it really worked. But have to configure the N900 also and not just the modem.

Facebook and Foreca widgets won't update when I'm in my home WLAN.

Update: I changed both phone and modem DNS settings to OpenDNS and the problem seems to be solved. I hope it stays. Thank you very much for everyones help in this thread.

I had the same problem with failed repositories and like maya once I changed the DNS settings to the OpenDNS servers everything started working again. I had also been having problems with Foreca not updating but this too is now OK. So what changed out there, because previously having auto DNS was no problem? Judging from other forums I have looked at this is quite a widespread problem and maybe needs a lot more publicity. Not everybody is a Linux guru, we are just mobile phone owners. Same with non-availability of PR1.2 for people who have Vodaphone 205 build even though we bought generic phone from - in my case - Expansys, and I am on O2. I do not fancy risking bricking it by trying to flash build 203, and I worked in IT for 20 years.

same problem here, because of this DNS problem, hope nokia does something about this quickly

My problems started when I moved to a new service provider (and a new ADSL router), as I explain here: http://talk.maemo.org/showthread.php?t=63416

Does anybody have any news about this?

Thanks.

Nokia may not know that your ISP/Service provider has faulty
DNS or some other DNS errors.

The DNS stuff has to be done by ISPs and not by the phone
producer.

I solved my problem editing resov.conf file. However, I'm not so sure about nokia's innocence regarding this problem.

Just ask yourself:
1) How should Nokia know about all the different DNS settings of all
the ISPs worldwide?
2) Nokia does not -as far as I know- provide internet services

These settings come from your provider.
If your ISP messes up his DNS then Nokia cannot do anything about this.

My ISP's DNS resolve correctly all the names in my PC and in N900 console (nslookup). The problem is in the 127.0.0.1 that nokia writes in the resolv.conf file (directed to the own N900). If adding to that file a DNS server from my ISP solves the problem (or an open DNS server), then I cannot be sure about who is responsible. Can you?