limitation cf_sql_varchar length

I have following cffunction in my cfc and calling from jQuery.

I use MS SQL Server 2008 R2 and the field is nvarchar(max) in the database.

The function fails to update when the string more than 800 characters.

I would like to know are there length limitation for cf_sql_varchar?

I tried to changed to CF_SQL_LONGVARCHAR, but it still fails when the text longer than 800 characters.

My users need to enter more than 800 characters.

Another issue is when the text has '%' then it wipe out all text and pass null to the MS SQL Server.

Any suggestion is appreciated,

Iccsi,

<cffunction name="Myfunction" access="remote">

   <cfargument name ="MyField" required="no" default="" hint="My Field">

    <cfstoredproc procedure = "MySP">

        <cfprocparam value = "#MyField#" CFSQLTYPE = "cf_sql_varchar">

</cfstoredproc>

</cffunction>