That seems more of an installation problem to me, especially the fact that the warning is about a "non-existent class" and inability to open a php file. The process I described is a normal part of the admin interface that should work perfectly well, I simply "discovered" that it could solve my particular problem.
Besides, disabling cache doesn't bring any changes to the frontpage.
I wouldn't expect any change in the frontpage just because you disable the cache. In my particular case I have a website that automatically aggregates news articles from other sites, without human intervention. That means new articles are written directly into the DB without any frontend or backend action, which as I understand is necessary for JRE cache to realize that it must delete a certain cache file (the frontpage cache file for example) - that's the reason why my frontpage stayed constant even when there were new articles in the DB. If you capture your articles manually then you don't need to disable cache of the front page if you keep JRE's default settings, because your very action of saving a new article will tell JRE to renew.