Sorry, Do you mean a Mac AND a PC or just a Mac.
Can you ask them what browser and what browser version they are using? And ask them if they can try an alternative just to see if it's a browser issue?
If they are using an old version of Safari then that could well be an issue.
We have had no other users saying this. Is everything else up to date? WordPress on 4.2.2? All SP plugins?
I am a Mac/OSX user myself so if you would like to set me up with an account I could take a look for you and try the action to see if anything is obvious. If so then Please PM credentials to both myself and to 'Mr Papa'. Please include in the PM a link to your site, a link to this thread and brief reminder of the problem. And one of us will take a look for you.
here is another email from the first student with the issue ....
"More strangeness...gave my computer-geek brother in Houston my login info. He had the same problem I am having. We both have up-to-date Safari. Is "Add Topic" the correct way for me to post? Just making sure I'm actually using the right button.
i have checked their membership status and all seems to be in order ..
there is something somewhere in the forum or setting that is an issue :<(
thanks so much for looking into this
thanks much ..
here is link
This is sort of an interesting one although probably not, sadly, for you.
The problem is caused by your WP theme but actually starts with a WordPress script error caused by your WP theme, But there is no way that this should be limited to Mac OSX users. It should effect all users.
The problem is described in this FAQ linked to below. Your WP theme (or another plugin) - is loading a non-standard version of the jQuery library.
Personally I would ask the theme authors, if they are at fault, to correct this.