i jsut got my own ns but when i try to change the configuration in my domain registrar, it kept saying failure to verify the ns i was given by my host...

why?

If you can, call your registrar and tell them your problem.

It may be at the point where you need to escalate the issue to a higher level of support than the registrar forms.

When registering name servers, or trying to use them the first time there can be other problems other than just normal propagation issues.