can't change customer account after installing https://

Hi does anybode recognize this problem: after we have a secure server en using https:// we cannot change a customer account anymore. In the fax field it says our username and we got asked again and again for the password of the customer. We need to change it now and then because of VAT rules in the EU. Does somebody know a fix for this bug?

The OC version has not been posted on the first post. No error logs provided since the change to HTTPS regarding customer accounts page and no config.php and admin/config.php files without database credentials posted.