unfortunately its the way browsers work that is the problem, we have applied a software upgrade, so the forum software is looking for certain files and routines as it loads a page.
Internet browsers try and be clever by remembering parts of a page that generally remain the same from visit to visit, unfortunately they remember bits even when they have been changed by an upgrade, thus they try and load the old version (that no longer works).
not keeping the software up to date is not an option, as it is upgraded to close off security loopholes that enable hackers to access the site and break things behind the scenes, once a vulnerability has been found, the forum software needs to have an upgrade to block up the loophole, so we cant just not update it.
the way around this is to clear the cache your machine holds for that webpage (this doesnt mean just clearing your history).
on chrome you would need to go to the 3 dots to get to the menu (other browsers have something looking like a gear wheel), select settings and then advanced settings to get to the clear browsing data page, then you could just select clear cached images and files (this should enable you to not have to lose all of the important login information from other sites.
Generally your browser will do a fresh download of the files every so often to ensure it is using the correct data, so we anticipate that this problem will resolve itself with time.
Unfortunately as its not a problem with the forum directly there is not a lot that we can do at this end to resolve this other than as we have already done, ie - encourage you to try clearing your cach.
If in doubt google for your specific browser- clear cache