Mail view not auto-refreshing, even w/ Fetch, but there are new emails not being shown

Mail view not auto-refreshing, even w/ Fetch, but there are new emails not being shown

I've observed this problem over and over again since beginning to use Zoho Mail (which, aside from some issues) I like better than Gmail.

The problem:
When in Mail w/ Inbox or any other folder view showing, new mail is arriving (I'll explain how I know that) but Zoho Mail is not auto-refreshing the view to show that there is new mail (bolded folder names or bolded new email in the view).  But if I click on another folder and then back to Inbox, suddenly all the new mail appears and is bolded and ready to read. 

The reason I know new mail has arrived is because my other devices that alert me to new mail (Blackberry and Gmail Notifier) all suddenly chime letting me know new mail has arrived.  So, I watch and wait and watch and wait for Zoho Mail to auto-refresh and show new mail, but nothing shows up (though sometimes it does seem to work, but usually not).  That when I try clicking the Fetch button, but it doesn't make the view refresh w/ the new mail.   It's only when I click another folder then click back to Inbox do I suddenly see all the new mail.

My browser is:  Firefox 3.0.10

Please advise.