Posting Issues

[rooster99ss]

Hi all, it seems our forum has recently encountered quite the little problem. When someone goes to create a new post and submit, it shows up with absolutely no content (i.e. no username, avatar, post count, location, etc.). Now, if I were to try and reply to that message I receive a "Sorry! This forum is not accepting posts at this time" message. As if that wasn't odd enough, when you go to reply to a thread that is already there (thread posted before these issues), it will actually show the Post Reply box as if nothing is wrong. When you try to hit submit on in the reply box, it sits idle until you literally have to just press back or close the window.
Today it seems we are getting a database error message. I will post it, as follows:

Database error in vBulletin 4.0.3:

Invalid SQL:
INSERT INTO post
(showsignature, allowsmilie, htmlstate, username, userid, title, pagetext, iconid, visible, parentid, threadid, dateline, ipaddress, attach)
VALUES
(1, 1, 'on_nl2br', '~chipsahoy~', 236, '', 'Test...', 0, 1, 424883, 10447, 1332864215, '24.249.55.27', 0);

MySQL Error : Duplicate entry '424889' for key 'PRIMARY'
Error Number : 1062
Request Date : Tuesday, March 27th 2012 @ 12:03:35 PM
Error Date : Tuesday, March 27th 2012 @ 12:03:35 PM
Script : http://lsxnation.net/newreply.php?do=postreply&t=10447
Referrer : http://lsxnation.net/newreply.php?p=424883&noquote=1
IP Address : 24.249.55.27
Username : ~chipsahoy~
Classname : vB_Database
MySQL Version : 5.1.58-1-log

I am stumped here. We recently lost our IT guy, so all of our current admins are scrambling to try and figure it out the best we can. Any and all help is GREATLY appreciated. Thank you for your time.

EDIT: I wanted to include that we are running vB 4.0.3.