I upgraded to 3.7.8 and observed "SSL protocol error" messages using the Silk browser on an Amazon Kindle HDX7 with sites such as https://www.c2kschools.net . No problems on a PC (using IE or FF). Downgrading back to 3.7.4.5 resolved the issue on the Kindle. Has anyone seen similar issues?

It might be possible that you are having a similar problem to the one discussed here http://forum.draytek.co.uk/viewtopic.php?f=14&t=19921 and http://forum.draytek.co.uk/viewtopic.php?f=2&t=19962

As you are not using a Plus model it may be totally unrelated, of course, but the fact that you are seeing SSL protocol errors makes me think there may at least be some link.