Untrusted SSL certificate?

[rogeranh@gmail.com]

Hi, am new to the forum and not highly familiar with OpenVPN. I have been using Private Tunnel with no real problems for about 2 months, but suddenly I cannot connect and my browser (IE9) has started warning me that the Private Tunnel website has an "untrusted SSL certificate" and suggests that my data may be intercepted if I continue (my browser says "Not Recommended" to continue, as this might be some sort of a trick). I am suspecting that my ISP has somehow hijacked my connection, or ??? Primarily, I need to use a proxy because my current ISP (Mega VNN in Vietnam) is blocking all access to Facebook, most of the time, and no doubt many other sites on direction from the national government here.
I also value my privacy and do not want my emails etc read illegally by anyone else.
Can someone please give me some ideas or suggestions on how to get this working again?
Many thanks,
Rikko