I had the same problem, try to use a date  format dd/mm/YYYY to cast  to the date type.
"20/2/2003" -> "20/02/2003"

Just tell me How to retirve text from a text Box and
cast it as a date.All my Attempts are Failing

I tried this

TextBox1.Text = FormatDateTime(TextBox1.Text,
DateFormat.ShortDate)
Dim ds As date  =
FormatDateTime(CDate(TextBox1.Text),
DateFormat.GeneralDate)
Response.Write(DateAdd(DateInterval.Day, 1,
ds))

I'v tried this :
dim ds as date  = DateTime.Parse(textbox1.text)

this should give you back a date .....