Yes, I do have C# code in custom page layout. And you probably thinking it is just another post about putting "<PageParserPath />" tag inside web.config.

But the answer is No. I managed to pin down the problem without having <PageParserPath /> tag. Well.. at least in my case.

Problem -

I got this error when I was creating a new publishing page, base on the custom page layout I have deployed to SharePoint site.

Solution

The reason I know <PageParserParth /> is not the answer to this problem is that, only two out of seven page layouts I deployed having this issue.

So I opened those "broken" page layouts from the site in SharePoint designer and found following code got injected to the bottom of my custom page layouts

I couldn't figure out how this got into my page layouts . But I am sure that SharePoint treated those "broken" page layouts differently as to other working page layouts.

I compared them side by side, read about PlaceHolderPageTitle is the root of all evil  post. I found in my broken page layouts they all got lower case <asp:content /> tag for PlaceHolderPageTitle place holder. So I changed <asp:content /> to <asp:Content />, and it fixed the problem!

Unlike Waldek's situation in the his post, I do have PlaceHolderPageTitle place holder in my page layouts. So this place holder is case sensitive? (because all my other place holders still use lower case <asp:content /> tag. )