We are getting the above on all doc types created. This has only happened this afternoon for no reason that we can see. Even if I create a fresh document type the Type dropdown is blank, then sometimes comes back then when trying to save I get the following error:

What can I check to try and figure this out?? 

[FormatException: Input string was not in a correct format.]
   System.Number.StringToNumber(String str, NumberStyles options, NumberBuffer& number, NumberFormatInfo info, Boolean parseDecimal) +7471335
   System.Number.ParseInt32(String s, NumberStyles style, NumberFormatInfo info) +119
   System.Int32.Parse(String s) +23
   umbraco.controls.GenericProperties.GenericProperty.get_Type() +56
   umbraco.controls.ContentTypeControlNew.saveProperties(SaveClickEventArgs& e) +1876
   umbraco.controls.ContentTypeControlNew.save_click(Object sender, ImageClickEventArgs e) +310
   System.Web.UI.WebControls.ImageButton.OnClick(ImageClickEventArgs e) +108
   System.Web.UI.WebControls.ImageButton.RaisePostBackEvent(String eventArgument) +118
   System.Web.UI.WebControls.ImageButton.System.Web.UI.IPostBackEventHandler.RaisePostBackEvent(String eventArgument) +10
   System.Web.UI.Page.RaisePostBackEvent(IPostBackEventHandler sourceControl, String eventArgument) +13
   System.Web.UI.Page.RaisePostBackEvent(NameValueCollection postData) +36
   System.Web.UI.Page.ProcessRequestMain(Boolean includeStagesBeforeAsyncPoint, Boolean includeStagesAfterAsyncPoint) +1565