I found this thread as I had the same exact problem with my oscommerce site running the paypal standard module redirecting to the paypal home page rather than the paypal checkout page. . .unfortunately there was not answer, but through some futher investigating, I found the answer and thought I would share!
My oscommerce site was installed in late 2007, so is an older version. . . my paypal module was using the url of
Code:
https://secure.paypal.com/cgi-bin/webscr
I needed to change this url to
Code:
https://www.paypal.com/cgi-bin/webscr
in my paypal.php file and now it works perfectly.
Apparently, paypal stopped using the secure.paypal url so it is not properly redirecting.
Hope this helps someone!!
Take care,
Kyla