Yes, I have the exact same problem. It appears in Opera and Chrome, too.
I’ve flagged this problem several months ago in these forums, as well as on the official Mailpress Google group, but so far nobody never gave me a fix.
Sadly, there’s no other newsletter plugin that has as many options as Mailpress at the moment… We have to stick with it for now.
I had the same problem. For me, the problem was caused by a different from usual setting of my blog charset. I used UTF8_unicode_ci in my database. You could check yours under wp_options in your database.
And the direct cause of the problem in question is the misbehavior of the function html_entity_decode, which appeared twice, around Line 821 and 836 in the document “mailpress\mp-includes\class\MP_Mail.class.php”.
A little reference to the function html_entity_decode could be viewed here: http://php.net/manual/en/function.html-entity-decode.php
I guess, in those two lines, instead of retrieving the charset from your database, configuring directly (e.g. ‘UTF-8’) could solve your problem. At least, it solved mine.
Good luck.
I’m having the same trouble.
It appears to be stopping if your database encoding doesn’t match up. I tried setting WP from UTF8 to UTF8_unicode_ci and the ‘Loading’ went away. However text no longer looked correct so I switched back to UTF8 in WP and still have the ‘Loading’ message.
When I looked in phpMyAdmin it looks to be defaulted to UTF8_unicode_ci for ‘MySQL connection collation’.
