String Was Not Recognized As A Valid DateTime?

working with dates is driving me mad I have the following function to parse al datetime strings in my project:

Public Shared Function ToDate(ByVal obj As Object) As DateTime?
If obj = String.Empty OrElse obj Is DBNull.Value Then Return Nothing
Return DateTime.Parse(obj.ToString)
End Function

Most of my date strings on my pc are "yyyy/MM/dd" and it parses fine. However on the server the dates are "dd/MM/yyyy".I tried this but it made no difference:

Public Shared Function ToDate(ByVal obj As Object) As DateTime?
If obj = String.Empty OrElse obj Is DBNull.Value Then Return Nothing
Return DateTime.Parse(obj.ToString, System.Threading.Thread.CurrentThread.CurrentCulture.DateTimeFormat)
End Function

on my pc if I assign DateTime.Now to a textbox I get 2011/05/31 08:02:00 AM for example. On the server I have my project the date displays as 31/05/2011 08:02:00 AM. Now I use objectdatasources to save the values to my database. Yesterday I was getting this error:Cannot convert value of parameter '' from 'System.String' to 'System.DateTime'until I formatted the date value like so:

Me.odsRates.InsertParameters.Add("CreatedDate", rt.CreatedDate.ToString("yyyy/MM/dd hh:mm:ss"))