This *seems* to be a recent R# problem (I'm running 1223) where certain kinds of editing of HTML (actually ASPX, ASCX) files cause a big VS repaint (certainly the whole project tree flashes).
The two things I've noticed cause a problem are:
Clicking with the mouse inside an element atribute value (e.g. an element class name)
Deleting chars from within an attribute value (but not inserting chars)
The latter is the big issue, as it makes editing html pretty much unbearably slow and flicker.
The problem goes away if the R# plugin is turned off on the VS tools->addins dialog.
This is an ASP.NET MVC application (so a Web Application Project)
Anyone else seeing this?