I'm going to mark this thread as [SOLVED].
I believe my proxy package is not large enough to support multi-threading.
See response from my proxy provider below...
"10 Threads Package is designed just for testing in SEO tools!
Regular browsers use more than 10 threads and you will get many errors if you use 10 threads package in browser.
You can check that in this article:
http://www.stevesouders.com/blog/2008/03/20/roundup-on-parallel-connections/
Please test proxies inside some SEO tool by actually using tool.
If you visit one webpage it has many elements (css, javascript, external images, etc.) that are parsed with parallel requests (threads) from browser.
So, for one single tab and one single page browser use a lot of threads - not just one.
That is why smallest "test" package of 10 threads is not enough for regular surfing in browser or any bot that use browser."
Thanks everyone!!!