There is absolutely nothing we can do to help you figure out why your FrontPage is not working with the latest TinyPortal if you have reverted back to TP 1.0 beta 4. The problem is probably, as you have surmised, with one or more custom block codes but there's no way to know this for sure. Since a Guest can't even see your FrontPage or your Forum, there is really nothing we can do to give you advice right now.
The best thing you could do is to clone your live site to a test site and then switch the test site to the default SMF core theme, uninstall beta 4 and install beta 5-1. If you do that, we will have something to work with. It also might not be a bad idea to turn off all of your blocks that contain custom code (everything but the standard TP blocks) and then turn them back on one at a time until you find the one (or more) that cause the problem. Only after getting everything to work right with the default SMF theme should you then switch to a custom theme and try it again.
The alternative is to post the code here for each of your custom code blocks so that we can check it on our test sites. Maybe we can find out which code blocks are the problem by doing that.