Long-ish post cannot be saved

I have run into a problem when trying to create a post containing about 84k of text, and noting else. I have duplicated this problem on both a WordPress 2.6.5 site and a WordPress 2.7 site.

I paste the text, and when I try to save or publish it, the post content box goes blank. Post revisions are saved, and after I click save twice, creating one current and one past revision, the past revision can be viewed and the content is there.

I have viewed the wp_posts table in phpmyadmin, and confirmed that the post_content exists for all revisions but the current one.

Restoring one of the past revisions results in the loss of post content for that revision. So to reiterate, regardless of which revisions can be viewed and restored, the current revision will never have content.

The 2.6.5 site has a pile of plugins, and the 2.7 site has only a few, with only 2 points of overlap between the sites. I have tried disableing all of the plugins with no effect.

Both reside on different hosts, one using linux, the other using freebsd.

I have tried this code in the htaccess files of both sites as it is the closest thing to a fix for this that has been suggested, and it failed:

<IfModule mod_security.c>
SecFilterEngine Off
SecFilterScanPOST Off
</IfModule>
php_value memory_limit 32M

Any help or suggesting would be appreciated. Thanks in advance to the community.