For those of you who still haven\’t been able to resolve this issue after trying all of the above solutions, I thought I\’d share mine with you, since it hasn\’t been mentioned anywhere before as far as I know.
I tried all of the solutions above, and none helped… my permissions are right, tried accessing the correct URL directly etc.
In the end I asked my server guys to look at it, and this is what they found, and how they fixed it for me:
\"There were no issues with the file itself, the problem was due to the URL being re-written incorrectly because it inherited the parent .htaccess in /shop/.
After doing some research on how to override the parent .htaccess in a subdirectory, we found the solution is just to add the following line in the sub .htaccess:
The URL loads successfully now.\”
For clarity, \"shop\" is my Magento root folder.
Original solution posted here: http://www.magentocommerce.com/boards/viewthread/21787/P45/