I can't submit an ad, extra reg form just clears

[JAM35F]

I'm trying to submit a new advert in the classifieds, but when I select to submit an ad I get a registration page asking me for address details etc. I'm sure I filled this in months ago but do it anyway, press submit(or whatever button at bottom is) and then all that happens is all the fields I've just filled in delete and I have t start again. But it never works!!!

What do I have to do to submit an ad these days?