insert and update via browser problem

Here's the deal: I have a mySQL database (version 3.22.32) that holds news articles. I've built a browser-based admin interface to insert, update and delete articles in this database. I've used the database and admin on multiple sites with no problems, until now. In my latest implementation of this "app," I can insert, update and delete articles of any size via telnet. Through my admin tool, I can insert, update and delete very short articles. However, I cannot insert or update (yet, I can delete) long articles via the admin tool. (When I say long, I only mean a couple-few paragraphs, not pages and pages of text.) The field is mediumtext, so that isn't the problem. On a different staging server, the admin tool works fine on any size article, so it's not my code. Originally, I thought that my ISP's firewall was blocking a certain size http send, but they've instructed me that the server my database is on is not behind a firewall. I've also gotten them to up the max_packet_allowed to 16M, and still the same problem. What else could be going on here? I'm really at a loss, and am desperately seeking advice from anyone that has even the smallest bit of input they can offer. Thanks in advance.