Why pay and suffer?
Use opensource like FluxBB (they are probably moving to Flarum
http://flarum.org/ with next version). You could see it (
http://demo.flarum.org ) now and possibly use it with a new site (A dediboard?) ;-)
I just clicked on a 60+ posts thread and it shows all the posts on the same page, its good, no 'next/prev page' links and URL changes on the address bar while scrolling down.
While It'd be great in an idealistic way, (and I hate to say this since they're not being helpful at all right now), the purpose of using a proprietary forum software is that it comes with support. There's someone we can talk to and actually get to fix these problems. Now obviously it's not working right now, but this is in theory why we use softare like this. Also similar reason why some Enterprise companies prefer VMWare over KVM or OpenVZ. VMWare have support staff available to fix problems whenever they happen.
Some of the big Open Source project do have people available for these, but most of the open-source forum softwares don't really offer this level of support (and a common attitude you receive is "just play with it" or "mess with it" and sometimes like we've seen with Sentora, "you shouldn't be complaining because it's free.. in fact you should be contributing because you're using our work"). It's just much easier for a company/organization to put the responsibility of support to an external organization that's much more knowledgable. In addition, our job and goal here is to focus on a cool community, not having to worry every other day about what will break on the back-end. With open source solutions, there's no easy way of getting this taken care of without a major time investment whenever something breaks.
So you want to know the actual definition of "Enterprise-Level Support" or just anything "Enterprise Level"? It's this. Not some person who knows how to install OpenVZ via a script and has their baby sister or some rando do their work for them by paying them pennies. Now if IPB Staff would get on the ball with this problem