Okay,
I'm running a fresh install (not a update/upgrade) of version 3.5.9 now, with the latest Dutch language file as default.
**1** Not only the huge amount of big sess*-files are a problem, because of them the PHP memory_limit is a bitch too. I've had to set it manually to 256M (Nope, 128 was not enough).
**2** The first translation in /FA/lang/nl_NL/LC_MESSAGES/nl_NL-2.3.0-3.php is
'' => 'Seems that system upgrade to version 2.1 has
\t\t\tbeen performed for this company already.<br> If something has gone
\t\t\twrong and you want to retry upgrade process you MUST perform
\t\t\tdatabase restore from last backup file first.Het lijkt erop dat systeem upgrade naar versie 2.1
\t\t\treeds is uitgevoerd voor dit bedrijf.<br> Als er iets is misgegaan en u
\t\t\twilt het opnieuw proberen MOET u eerst de database herstellen van de
\t\t\tlaatste veiligheidskopie.',
It looks to me as an translation-bug. If not, by now people should have upgraded from v2.1. Anyway, this text is causing the sess*-files to grow even much bigger. I've deleted this line from my language file.
**3** I've tested the file you've mailed me again.
With debug set to 0, I'm only getting empty pages, with an empty source too, so no output at all
With debug set to 1 or 2, I'm getting this error message "PHP Fatal error: Call to a member function has_key() on a non-object in /**path**/includes/lang/gettext.php on line 404"
But .... the sess*-files are pretty small.