404 error on checkout, SSL or htaccess culprit?

hi,
i was working for a client’s site and this is my first time working on a magento project. my date line is 2 more days, and i have complete populating sales item, plugin config and getting my webhost to install SSL. all is working but until just now when i try to do a ‘mock’ order and checkout, the page give me a 404 page not found error.

for your info the checkout link that generate that error is https://www.mysite.com/checkout/onepage/.

i checked my System > Config > Web, my secure & unsecure url is https://wwww.mysite.com/ and my Use Web Server Rewrites is set to YES. the rest of the settings remained untouched. Also i have deleted the caches in var/cache but still the checkout is unfruitful. I also checked that my .htaccess is intact too.

Any advice on this will be very much appreciated as i am 2 days shy from launching it.
thanks.

check this once http://www.magentocommerce.com/boards/viewthread/19132/

thanks for the info. however the link is for google checkout error which is different from my situation.

i found the solution for this. for those who is experiencing the same thing, here is the solution:

go to System > Config > Web > Secure > Base Link URL and key in your full secure URL for example https://www.mysite.com

that will solve the problem.