Awesome, thank you.
I'm actually ignorant as to why it happened, but the post auto-increment value was at over 1.2 million and is now far higher. I couldn't say if it has to do with vBulletin or not, but we have had some odd server issues recently that have been thrashing mysql that are likely to blame.
Code:
mysql> select postid from post where postid > 1254039 limit 4;
+------------+
| postid |
+------------+
| 1254040 |
| 1059793148 |
| 1059793149 |
| 1059793150 |
+------------+