Thanks wirehopper, that did the trick and now the form is fully processing.
However, it looks like either the preg_match or the sanitizer script is inserting the letter "x" into the beginning (and other places) in the fields. I'll see if I can figure out the problem but here is what it's doing:
As a test I entered the following into the forum; all without the quotes and the output was placed successfully into the MySQL database:
First name: "Franky"
Output: "xFranky"
Last name: "Miller"
Output: "xMilxer"
Email (same in both fields): "franky@mailinator.com"
Output: "xfraxnky@xmaixlinxator.xcom"
If I figure out a solution I'll report back.
EDIT: I used echo so I could see the variables pre- and post-sanitize by simply echoing both the variables and it looks like the sanitizer is placing the "x" into the variable, just FYI.