Hey Suzy. I gotta tell ya, in all my 9 years of ColdFusion development, I have never once used the <cfinsert> tag! I had to look that one up for ya

lol. Always just used direct querying instead.
But after checking it out, I don't think that it's going to work for you in this case. You might have to write out a full database INSERT statement in a <cfquery> tag.
Try this code:
Code:
<cfset dob = form.birthMonth & "/" & form.birthDay & "/" & form.birthYear>
<cfquery datasource="062105cs06sr">
INSERT INTO users (
username,
createDate,
password,
firstName,
lastName,
dob,
town,
postcode,
bio
) VALUES (
<cfqueryparam value="#form.username#" cfsqltype="CF_SQL_VARCHAR">,
<cfqueryparam value="#form.createDate#" cfsqltype="CF_SQL_DATE">,
<cfqueryparam value="#form.password#" cfsqltype="CF_SQL_VARCHAR">,
<cfqueryparam value="#form.firstname#" cfsqltype="CF_SQL_VARCHAR">,
<cfqueryparam value="#dob#" cfsqltype="CF_SQL_DATE">,
<cfqueryparam value="#form.town#" cfsqltype="CF_SQL_VARCHAR">,
<cfqueryparam value="#form.postcode#" cfsqltype="CF_SQL_VARCHAR">,
<cfqueryparam value="#form.bio#" cfsqltype="CF_SQL_VARCHAR">
)
</cfquery>
The <cfqueryparam> tags are to validate data, and protect you from any SQL injection attacks. You can google that if ya like (can be a big database security issue), but suffice it to say, it is always best to use them
Hope that helps.
-Greg