Hi, sorry for not having posted the system specs before. I've been accessing the internet at the local library and at the university and didn't have the laptop with me when I posted.
You can now check the specs on my profile page. I've added all I knew. If you need to know something more specific, please tell me how to find out that info.
The only connection that's giving me trouble is the mobile connection. The modem is a USB stick from HUAWEI, but I don't know its model name. I've searched on the carrier's website and can't find it anywhere. The box where it came also doesn't help. It's known as 'O2 Surfstick 3', but that's not the model.
I've been using this connection since October without experiencing any problems. 3 days ago it started hanging a few minutes after the connection is established. Restarting the connection would help, but after a few tries the minutes turned to seconds, or it doesn't work at all. The connection is active all the time, but I can't access anything with it. I also get that yellow caution sign that Shidaw complained about. When running the troubleshooter, either it reports something wrong with the DNS servers, or it reports no problems at all.
I tried adding the Google DNS servers manually (8.8.8.8 and 8.8.4.4) since it seemed to have problems w/ name resolution and the first few times all went well. Later I got exactly the same problem as before, and whenever I looked at the IPv4 settings, the DNS info was gone. I repeated the process several times, and the addresses would always vanish after a while. I seemed to be able to access websites while the info was there, but I am not sure.
What worries me now is that about an hour ago I tried to connect with this USB stick and it worked. Actually that's the connection I'm using right now, without any DNS info set by me. When it comes to computers, nothing frightens me more than an intermittent failure
I'm sorry, reghakr, but I cannot try your method now, since the connection seems to be alright. Unfortunately I forgot to ping an address instead of a name when I experienced problems. If it happens again, I'll try it and post the results.
Do you think the application for the modem provided by my carrier is resetting the DNS address fields? If so, why just now? And why did it first take dozens of minutes to do so, and later just a few seconds, or none at all?
Thanks for your replies!