URL blocked by Network Shield

I visited a model rocket site and the following URL was flagged by Network Shield.

http://www.aerotechstore.com/

I checked the URL with Securi and it came up clean.

http://sitecheck.sucuri.net/results/www.aerotechstore.com/

What would cause this URL to be flagged by Network Shield.

and what does avast say?..a screenshot of the pop up?

https://www.virustotal.com/url/afbda91f4cb87838f4ed3343e5d4d5542b9f4ee75b758e964d4f5384bb6d648e/analysis/1352326895/

Thanks for the reply. Here it is.