It seems strange that this error message would appear in only certain browsers (but not others).
I would expect such a problem to affect all browsers (or none).
Try clearing your Safari browser's cache before reloading your gallery's web page to see if this helps.
Also, if you have any extensions installed in your Safari browser, try temporarily disabling them to see if this makes a difference.
If you continue to experience difficulties, please post the URL to your gallery's web page so that I can take a look at the problem for myself and hopefully help further.
In the meantime, maybe this FAQ will help:
When I view my gallery I see the message 'Config file not found'. How do I fix this?