I have exactly the same problem described in bug 22427 (seems nobody is looking at that one anymore, thus I'm submitting this dupe)

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I am currently experincing some problems with missing post form data. 

There seem two be 2 problems:
1) When a variable is long (for example a textarea and lots of text is
in it), the post data is not sent.
2) Sometimes even with small textarea, the post is still not outputed,
but if you hit refresh and click reload post data, it sometimes works. 

I have also set the max post size to 20MB which should be plenty for
just text.

I seem to have this problems on all browsers / computers.
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I'm experiencing this when trying to install postnuke: The first screen (Language selection) sometimes submits correctly, sometimes it doesn't. The second screen (with the GPL license agreement in a textared) NEVER gets submitted correctly, the POST variables remain empty.

I DO have register_globals set to on and post_max_size = 10M which should be sufficient.

My webserver: Apache/1.3.27 (Win32) mod_gzip/1.3.19.1a PHP/4.3.2. (using the PHP SAPI module) The problem also occurs in PHP/4.2.3 and PHP/4.3.1.

If you need any further information or want me to test something, please let me know. This bug is very annoying and the way I see it I'm not the only one experiencing it.