Google instant preview comes blank in some pages and posts

I am running a site that is based on WordPress and heavily invest in promoting it on Google SEO. The problem I face is very odd. In Google Instant Preview some of the pages (homepage among them) is coming blank in the article area. i.e. the header, footer and sidebars are shown but the main part, the body is missing.
To see this effect, simply click here and check the instant preview of the home page. Don’t panic! the site is in Hebrew, but the visible effect is clear.
The problem repeats itself in 41 out of hundreds of pages and posts in the site.
Does anyone have any idea?