Supporter Paypal transaction pending

When I try and upgrade a test site to become a supporter the transaction is not completing.

After I have gone through the sandbox purchase process and go back to the test site I have the following message above the supporter payment options:

Note: Last transaction is pending. Reason:

The reason is blank.

So it seems like the payment is recognised but somehow listed as pending.

When I got to http://mysite.com/supporter-paypal.php (using firefox) I correctly get this message:

Error: Missing POST variables. Identification is not possible.

For some reason Chrome always shows this as a broken link.

I have disable all plugins and only enabled Supporter and still have this problem.

I am using WP3.0.1 and BP 1.2.5.2