[TYPO3] Realurl not working in one typo3 installation, yet working in another on the same domain.

[Vincent Mans]

Well, after upgrading, the problems persist:

* first, links seem to go well
** after a short while, the links are replaced by numbers (e.g. /34/
in stead of /nice-and-readable/)
*** this starts at homelevel, and drips down into the whole
installation (on the top level all links are replaced, but going to a
page on a deeper level, the correct situation still exists); the
rootpage is set; the rootpage is also a shortcut to the entry page
with content, it looks like passing through this page breaks the links
(for example if this page is used as target for home and then
redirects to the actual home content)

The database is not affected, it are only the links on the website (in
text and documents).

What could cause this? Does something relevant happen, just before the
HTML is rendered to the frontend?

I have 2 solutions, but I don't know yet if they are successful over a few days:
1 - making less levels (not good)
2 - using a RealURL prevars for L=0 seems to stabilize the situation