On an RH7.2 box, running the latest RH released versions of PHP (4.1.2), PHP-MySQL (4.1.2) and MySQL (3.23.58) I have installed MediaWiki 1.4.7, which initially appears to be working fine. However, all attempts to edit pages, anonymously or logged in either as an ordinary user or WikiSysop, produce the same result. Pressing 'Save page' has the same effect as pressing 'Show Preview'. The Preview doesn't contain either the old or the new page, but once again offers the option of either a Preview or a Save.
The symptoms sound a little like those in this thread: http://mail.wikipedia.org/pipermail/mediawiki-l/2005-April/004840.html
I tried adding the session_save_path(...) statement to the end of LocalSettings.php, but saw no change in behaviour.
Chris