Problem browsing https site

Hi to all i'm unable to browse an ecommerce site wich is secured in https.
The site is https://ecommerce.infocert.it/legalmail/lmrinnovo; my untangle version is Build: 10.0.0~svn20131211r36618release10.0-1squeeze.
I have followed instructions to import Untangle cert into PC with AD policy domain (i dont have HTTPS inspector installed) in CHROME i have the following error (see image 1)
image1_chrome.png

instead in Firefox i have the following error
image1_firefox.png
My machine is win 7 64bit (but i have same problem in all pcs xp linux ecc) my browser versions are
Firefox 26.0
Chrome Versione 24.0.1312.57 m

Thanks in advance for helping me. Best regards Davide.

Attached Images

• image1_chrome.png (5.4 KB)
• image1_firefox.png (6.0 KB)