Problem with tag prefix

I have a user control on my form and to reference it i am using @register and a tag prefix, but it is complaining that it cant find it (when looking at the code).
 
When i run the page i get:
 
Unable to cast object of type 'ASP.ccweb_modules2_complaintdetails_cc_detail_defect_edit_ascx' to type 'CCS.EISS.Portal.SystemFrameworks.AP_SF_Control'.  
[InvalidCastException: Unable to cast object of type 'ASP.ccweb_modules2_complaintdetails_cc_detail_defect_edit_ascx' to type 'CCS.EISS.Portal.SystemFrameworks.AP_SF_Control'.] CCWeb.CC_ControlLoader.LoadControl(String PageControl) in C:\source control\Europortal\Enhancements\Customer Complaint\Web\CustomerComplaintsWeb\Modules2\CC_ControlLoader.aspx.vb:67 CCWeb.CC_ControlLoader.Page_Load(Object sender, EventArgs e) in C:\source control\Europortal\Enhancements\Customer Comp ...