only thing I can think is that installing it using the update panel has caused the problem. I wonder - have you restarted the server at all since you installed Twiggi ?
Could it be that the templates have not been expanded properly by installing it through the panel? Have you tried even just restarting Apache if you dont want to restart the entire server?
The rpm you installed creates the databases etc for you as part of the install procedure.
The install procedure I had to follow was simple - copy the rpm onto an ibay called rpms that I use for dumping them onto the server then
cd /home/e-smith/files/ibays/rpms/files
rpm -Uvh *.rpm
Then we were able to access our mail through
https://servername/twiggiBy default it only works on https and not for http.
Thats about as difficult as the install procedure got.