This question has been answered by meltingdog. See the first response.
Did you just move the site? Or did you follow all the instructions here?
http://rtfm.modx.com/display/revolution20/Moving+Your+Site+to+a+New+Server
Lot's of things besides the URLs need to change. Your site is in a completely different location.
- The four config.core.php files likely have the wrong path to the core
- In config.inc.php, you have to change the paths in addition to the URLs
- The path in the MODX workspaces table needs to be changed.
Running setup in upgrade mode might take care of everything for you.
If the message is actually "Access Forbidden" it suggests a problem with the permissions or ownership of the directories and/or files -- that's not a MODX message (you'd be seeing "Access Denied" from MODX). I'd compare the file and directory permissions with those in the working site.