"Could not reformat the document" in ASP.NET, VS2008

Did get the problem today.

My solution: Restart Visual Studio

Usually this sort of behavior is caused by invalid code. It may only be invalid HTML causing it which would still allow the program to be compiled.

For example, if tags are mismatched like this the IDE cannot reformat it.

<div><h1>My Title</div></h1

Check your warnings to see if there are any entries pointing towards mismatched or unclosed tags.

There's probably some malformed markup somewhere in your document. Have you tried it on a fresh document?