This error drives me nuts frequently when editing a .ASPX page. Its really weird.
And of course I have this code at the top of the page:
<%-- The following line works around an ASP.NET compiler warning --%>
Today I figured out that sometimes I think VS just gets confused. For instance, this line might work just fine:
<%= SomeVar %>
Then again it might generate that error above. The only real fix I have found for those lines is to replace = with Response.Write which = is a shortcut for anyway:
<%Response.Write( SomeVar) %>