I've been running WordPress with Apache 2, PHP5 and MySQL 4.1 since the alpha stage with no problems (aside from bugs in the alphas, natch).
Peering through some of those posts, a couple of things spring to mind.
If WP is consistently sticking a
\ in front of
" characters, check to see if "magic_quotes" is on or off in your PHP config. I believe it's behaviour changed between PHP4 and PHP5, so try setting to the opposite value and see if that gets fixed. PHP5 also has a PHP4 compatibility mode, but my understanding is that it's not great and can cause it's own problems. If you're running PHP5, then PHP4 compatibility should be turned off.
PHP4 and MySQL 4.1 don't get along well without a little hacking on MySQL, so it's not a recommended combination. People with login or certain installation problems might be experiencing a symptom of this configuration.
If you're running Apache under Windows, it can run either in the
system account or an account you specify. If you've installed Apache with it's own Windows username (or if your host has), this might be a simple permissions problem that can be solved by elevating the Apache user's permissions on the folder containing the
htaccess file. Windows can also have difficulties with files that only have an extension for a name (like
.htaccess), so that might be a problem if the latest updates and versions aren't installed.
Good luck :)