Try logging out of the forum, close the tab with the forums open, then go to settings in your browser and clear browsing data (On chrome it's, Settings (3 dots upper right corner of browser window), then click "show advanced settings" at the bottom of the page, then Clear Browsing data.
Once you do that re-visit the forum (while logged out) see if it seems fast.
Then try logging in again. If it's slow only while logged in you'll know it's your user profile.
Hope that helps!
Buzz