Strange behavior in WebHandlers

Update: clearing the cache and restarting VS makes the problem go away temporarily,
but with this particular file, the problem reoccurred within about a minute
of making further changes after the restart.

Build 223, VS2005, Solution contains 1 web project and 1 class library

Hard to pin down exactly what the cause is, but I regularly see this
behavior after editing an IHttpHandler (.ashx) file. For some reason,
R# highlights every line in the file with the red-wavy underline, with
the only clue to what's wrong being "unexpected token". When I click
on the little red bar to go to the error location, it tells me that
the WebHandler declaration is the problem -

<%@ WebHandler Language="C#"
Class="Unsd.Mi.Web.Handlers.CountryDataHandler" %>

See attached for screenshot. The behavior is not consistant; some
handlers go uneffected, but in some it happens all the time.

The code compiles without any errors.