Try booting into Safe Mode. There look at what's in the Startup subfolder in your Start Menu and remove anything suspicious from it. Also, run msconfig32.exe and go to the Startup tab and do the same there.
By "suspicious" I mean anything that you have just installed - if you can remember, anything shortly before the problem started - and that you don't really need.
Also, if you don't have it, get the free Codestuff Starter utility and install and run it. In addition to the above it shows you everything that gets started from the Registry. You can disable anything suspicious from within Codestuff Starter. I think Codestuff Starter will run in Safe Mode but I'm not sure.
Finally, if you have Spybot turn on the option to run TeaTimer there. It notifies you when anything tries to change these and, I think, other critical areas of the Registry - and gives you the option to allow or deny it.
You appear to have some kind of malware that is getting itself started at boot up and is probably trying to access the Internet - to which you are probably not yet connected - and thus giving you this problem.
HTH
By "suspicious" I mean anything that you have just installed - if you can remember, anything shortly before the problem started - and that you don't really need.
Also, if you don't have it, get the free Codestuff Starter utility and install and run it. In addition to the above it shows you everything that gets started from the Registry. You can disable anything suspicious from within Codestuff Starter. I think Codestuff Starter will run in Safe Mode but I'm not sure.
Finally, if you have Spybot turn on the option to run TeaTimer there. It notifies you when anything tries to change these and, I think, other critical areas of the Registry - and gives you the option to allow or deny it.
You appear to have some kind of malware that is getting itself started at boot up and is probably trying to access the Internet - to which you are probably not yet connected - and thus giving you this problem.
HTH