I don't think it is me... I ran a number of web tests from US, Australasia, Asia, Europe and all of them came back with load times greater than 10 secs/page. This means that often the web software times out and just returns the front page, not the page you linked to. While Xenforo is really pretty, it also has a huge number of instances of people going : "Site is really slow". Have you had anyone look at your installed options, your cacheing, your PHP and SQL config? It has gotten to the stage that, while I would love to contribute to the forum, I am sick of spending half an hour to do something that should take 3-4 minutes. You can forget things like loading updated pictures, the system even struggles to refresh the alert list at the top right. I have learned through bitter experience to copy my post before pressing 'submit' - too many times have I done so only to lose the whole thread. It's almost like you are running on $1 a month shared hosting, it's that bad... (While I was writing this, something that is relatively trivial on most forum apps, I got the dreaded 'red screen of death' - where Javascript just gives up.)
And... after submitting, the site timed out and dumped me back to the main openbuilds.com home page. Normally I wouldn't bother, but it's so bad it really must be hurting your business.
The time between the first post and the second is how long it took to reload and get back to the point you could re-enter another message. nearly 19 minutes of frustration.
Sometimes on Firefox the website is redirecting me to the main page, logged off, and there is no way to login again. But when it does that, I just login with Chrome and all's fine, and some time later the page works again on Firefox... but the website is never slow with me...
If 5mb/sec isn't enough, then maybe it's a problem. But, I don't have this problem with any of the more than 20 forums I frequent, nor do I have a problem with open build parts store. FWIW, I've been a Comms specialist since around 1975, been active on the Internet since the mid 80s and worked developing wifi systems before it was 802.anything. It's not my internet connection.