It's a rewriting issue, I've just had it too. Though my installation was a bit long winded due to me installing on debian.
In /etc/apache2/sites-available/
the default set up looks like this (at least on my set-up with phpMyAdmin):
NameVirtualHost *:8080
NameVirtualHost *:443
<VirtualHost *:8080>
ServerAdmin webmaster@localhost
</VirtualHost>
<VirtualHost *:443>
SSLEngine on
SSLCertificateFile /etc/ssl/certs/cert.pem
ServerAdmin webmaster@localhost
DocumentRoot /var/www/
</VirtualHost>
ScriptAlias /cgi-bin/ /var/www/cgi-bin/
<Directory /var/www/>
Options Indexes FollowSymLinks MultiViews
allow from all
AllowOverride All
</Directory>
Remove:
<Directory /var/www/>
Options Indexes FollowSymLinks MultiViews
allow from all
AllowOverride All
</Directory>
And replace with:
<Directory /your/forum/path/>
AllowOverride All
</Directory>
Initially I had this below the /var/www
, but it needs to replace it
Try it anyway, it's the only thing that worked for me