Payments Reminder Paying using secure site

We have a payments reminder setup where clients are redirected to our customer login page. The page tells them how much they owe and when they login they are able to make the payment but it hangs when getting to secure payment page. Payments are redirected to https://secure.authorize.net which is were the whole process stops. Gives error saying page timed out taking too long to load. We are allowing the url and ip address in web proxy and firewall but still will not load. It shows 0 hits in web proxy. If the payment page is refreshed then it will show up as an error but will show up after refreshing a third time. Any help would be appreciated.

Thanks.