It's hard to tell what's the issue in your case off the bat. Keep in mind that pixel shader effects can increase the VRAM demand as well.
was under the impression that all textures were purged from the cache whenever a new layout was loaded - is this not the case?
I'm fairly sure that you're already familiar with this but you can control the texture loading in the application settings, layout settings and also through events. So it's really up to you how to deal with the texture loading.
<img src="http://i.imgur.com/XXpe0.png" border="0" />
<img src="http://i.imgur.com/EgdeN.png" border="0" />
<img src="http://i.imgur.com/amLkh.png" border="0" />