More often than not, when I'm streaming videos online (through such sites as hulu & justintv), it's choppy & freezes a lot. This is a recent problem & occurs when I use both IE & Firefox. I doubt it's an internet issue, as I don't have any other internet issues & all sites seem to load fine. Any ideas what the issue(s) could be? Possible bug of some kind?

Streaming media is about the most internet intensive application you can run.

Loading a webpage takes a small fraction of the bandwidth that streaming media does.

It is impossible to say something like webpages seem to load fine so it can't be an internet problem, when talking about streaming media. Choppy and freezing streaming media most certainly is an internet issue. Webpages may still load fine because they require next to no bandwidth whatsoever.

You need to run some tests on your connection and determine what is happening.

Various VoIP tests can provide detailed analysis of your connection that is similar to the requirements of streaming media.

Here's some sites that may be of interest to you:
http://myspeed.visualware.com/voip/
http://www.testyourvoip.com/
http://www.speedtest.net/