Paypal express stopped working- only get so far!

Ok so I had paypal express working a few days ago, and now... it's not.
here's a run down of what happens:

1. Buyer clicks on paypal button on shopping cart page (as opposed to 'checkout' button).
2. Buyer is taken to paypal login page.
3. When buyer logs in to paypal they're then taken to a page listing payment method/postal address/contact details (this is the information that will be used to create the account for them). Click continue.
4. Taken back to the webstore showing a payment information screen, listing sub total & postage and an area for special instructions. Click continue.
5. Order confirmation page showing billing/payment info, cart content and final 'confirm order!' page. click confirm order.
6. taken to main paypal login page- ie the actual paypal.com page.

IPN and API's are all set up correctly, and it works fine if you sign up for a store account before checking out with paypal.

zen version 1.3.8

curl test and IPN test both have been done, and say everything's ok.

Further investigation.

I've compared (using beyond compare) the ipn_main_handler, paypalwpp.php, paypal.php, and all other paypal orientated files in the paypal area of modules & payment. No difference.

Checkout works fine if you're already signed up for an account and just choose paypal as a payment method, only breaks down if using paypal direct from shopping cart.

The confirm order from the point of view of already having an account and following a traditional route takes you to a 'http://yourdomain/yourstore/ipn_main_handler.php' file location, whereas the confirm order from the express checkout points directly to https://www.paypal.com/cgi-bin/webscr, thus customer ending up at regular paypal index.

seem to have resolved my own problem.
Through reading about similar problems with the paypal express module showing different payment types such as showing COD or cheque even though it was paid through paypal, I tried a few of the same resolutions. The main one being to not just deactive (amber) but completely uninstall (red) all other payment modules, even though the only other module I had deactivated was the paypal IPN.
That seems to have completely resolved the issue.

Hey finest, I'm having a very similar issue. Paypal takes me back to my store when it should be paying the bill...and makes me walk through all three confirmation steps in the store, before finally getting it done.

I have pictures up here....
http://www.zen-cart.com/forum/showthread.php?t=99606

I definitely have gift certificates and coupons disabled and this is really frustrating...any suggestions?