On my stock Viewsonic G, I have recently been getting a "Not Trusted Server Certificate" error that keeps me from accessing the Amazon market, gReader and Zinio in the Readers Hub.
Same problem on two different wifi systems I tried it on.
I did, but my google-fu has failed me. However, I did manage to accidentally fix it. I noticed that the date was wrong on the tab ... fixed that and the certificate problem disappeared for all the involved apps.