Don't know but when adding stuff programmatically ( as I am doing at the moment also) I have found THAT error, the old Obj ref not set, popping up everywhere.

I tend to stick a lot of "new"'s everywhere.
I use c# so am not on the ball with VB sytax.
In C# I would use
System.Web.UI.HtmlControls.HtmlControl StyleSheetURL;
in the declaration and then instantiate as a 'new' in the initialise
StyleSheetURL = new System.Web.UI.HtmlControls.HtmlControl();

Then you have an object. Seems to clear a lot up.

Don't know what the VB syntax is though ??

If its only happening in one of the pages  then there's something wrong with that page specifically, surely. you've probs leant on the keyboard with that page open !