Check these tips:

I use NavigateURL()  all the time to return me a string with the correct URL of the requested object (did you use it with tabid: Public Function NavigateURL(ByVal TabID As Integer) As String)

In your host settings you need to check "Use Friendly Urls?", if you want navigateurl to return you a friendly url

if your control is not a viewcontrol EditUrl can give you a beter result

strKeyValue = gridview1.selectedvalue
response.redirect ( EditUrl("edit", strKeyValue, "", "filter=" & strFilter) )