There is literally no help for this particular question. But, i was able to turn of validation on the page to get around the issue. If you turn of page validation though you need to write in the code to replace the dangerous characters with their html equivelant.
To turn of page validation, try this...
Modify your web.config file to allow you to turn off validation for a single page.
Then add the ValidateRequest="false" to the page directive
<%@ Page Title="" Language="vb" AutoEventWireup="false" CodeBehind="page.aspx.vb" Inherits="project.page" ValidateRequest="false" %>
This should keep the page from validating before the postback happens. Then you can let your code modify your text accordingly.
I hope this is helpful.