I'll assume you have FP 2002 extensions installed and no changes have been made to the physical folder permissions (ACL's) where the sites are stored.
A couple of things you can check:
Open a browser and enter:
This will bring up the administration page for that FP site. The top of the page will be titled:
FrontPage Server Extensions 2002
Site Administration for "
From here double check the permissions and roles for the servername\logins who should have author rights to that particular site. I'm assuming you have unique logins for each client and their corresponding FP site, (and you should) for security.
Click on the login having trouble, and make sure that "Advanced Author" is selected. If not, select it and submit the new settings.
Recalculate the site and then have your client login and do some authoring. Also, make sure the Everyone group has read access to the physical web folders. This should take care of the issues you've described...
Also, here's a tip:
Never upload files to a FrontPage site using Windows Explorer or an FTP client. Use only FrontPage. I've had to correct many a hosed FP site where authors make changes on a local server they are designing their site on, then try and upload it to a share on a testing server using Explorer or an FTP client on a remote server. It's not pretty.
Hope this helps