If you have never used those names that are coming up on GMX before then it must be a local issue combination of cookies, caches and the browser using its autofill memory.
If you have used them before on GMX then check GMX settings about not adding contacts or whatever
use something like CCleaner its free to clear all caches then try it and see if the details come up, i'll be extremely suprised if they do
also to be double sure you need to go into your browsers settings and tell it not to remember passwords or any thing like that and turn off any autofiill.