Hi Nat0,
I had to move the forum software from /forum to the root directory when I retired the old front page.
I believe many of the previous links were of the format: forum/forums/
If you remove the /forum part so it's just /forums/ it should load those pages for you, but if not please copy / paste the tabs here.
Google should reindex the site over time and fix the broken links, but I may set up a redirect to handle it.
Right now the only redirect I have is from /forum/ requests to go to /forums/
I will need to check the server error logs to see how often old URLs are being accessed.
I know it's a pain, hence why I put this off for ages, but after everything slowed down I realised I couldn't postpone things any longer.