There are compatibility issues with some browsers with the Allow-From parameter for X-Frame-Options response header, chances are you are dealing with a browser which does not support it.
Ideally try this command to see the headers output and make sure the setting you made is being used:
curl -I http://yourserver.example.com/exceptionpath/
If it is, instead of setting that other header you may also want to unset that header in that directory to avoid compatibility issues with that parameter:
Header unset X-Frame-Options
or if the above is not being applied:
Header always unset X-Frame-Options
Sidenote: If you are the admin of the site you don't need to use .htaccess if you have access to main configuration files, set in the appropiate Directory entry instead. Disable .htaccess files altogether with AllowOverride none. Configurations will be simpler and you will gain a bit of performance by not forcing httpd to constantly read that file several times with each hit.