If you get to Yahoo through a bookmark, check the bookmark and be sure it is the correct link.
Next, make certain that the Browser not "auto-completing" the URL to a Nederland version, by typing your usual Yahoo link and before you press Enter, look for added or changed letters in blue.
Next, suspect that Yahoo is using cookies to detect that you really want the Nederland version, and sends you there instead. I would go look at the Yahoo cookies and delete some. They will grow back soon enough.
If still no joy, there may be darker issues at play.
Is your system software fully up-to-date with Software Update? If not, now would be a good time to do that and get any detected malware removed at the same time.
Are you using the correct Domain Name Server (DNS) numbers your ISP gave you to look up Internet "phone numbers"? Check them against the ones your ISP says to use, which should be readily available in your ISP help pages. NO valid DNS number begin with 85.xxx.yyy.zzz.
If you are in the US, you can use OpenDNS or Google DNS standard DNS numbers. In South America, Africa, Europe or Asia, these may cause additional delays.