I can only post short entries

Out of nowhere, I can’t post anything longer than a few lines. Pressing [ENTER] to begin a new paragraph seems to play a role in the failure, but so does overall character count. I’ve tried different PC’s, IE6, IE7, FF2, Opera 9.2 and Safari 3, deactivating all plugins, repairing SQL, dropping SQL tables, installing into a new directory with a new SQL DB, but it fails everytime. If I get a short post to stick, great, but then I can’t edit it. Also, when it doesn’t post I get redirected to the Manage page, but there’s no sign of the post I just submit.

My ISP says it’s not them. Hard to tell.

For the record, new install into new directory, with a new DB, no plugins, default theme and I can’t post more than a few lines.

The fresh install is for debugging this issue, so if seeing what I mean is necessary I can post the URL.