Flarium forum was in a different thread, however AIM Support did comment that its still 'beta' software. Fully respect that comment as you don't really want the headache of additional fixing of issues and things that are just plain broken.
Flarium really does 'look' nice and i still really like it.
Another one is vbullitin which has a paid model and pretty feature packed the last time i looked. Setup and management was fairly straight forward.
Software aside, could it just be a miss configuration somewhere that's giving people the main gripe point when replies 'disappear'?