I've tried two different webcams with two different computers, and oddly enough, both do the same exact thing:

I'll plug them in, start up webcamming with someone, it will work fine, then freeze once, then unfreeze, freeze again, and then it's good to go for hours without any complications. I find it extremely odd that it has happened with two separate computers, and two separate webcam units.

Any ideas of what it could be and how to remedy it?

What do you mean?

Like there is a short pause and the frame it paused on is 'frozen' in place for a short period of time?

Then it starts up again, and then repeats the process?

After which it will behave normally for any amount of time...does that include other sessions with the camera or is this actually session by session problem?

What do you mean?

Like there is a short pause and the frame it paused on is 'frozen' in place for a short period of time?

Then it starts up again, and then repeats the process?

After which it will behave normally for any amount of time...does that include other sessions with the camera or is this actually session by session problem?

Yes, frozen in place for a period of time...I'll say 30-60 seconds. I'll leave it be, without closing it. Then it will resume normally for another 15-30 seconds, and freeze in place again for 30-60 seconds, then resume normally infinitely until the session is exited.
If I were to close the window, and open it again, the same procedure would take place. It is rather annoying, as I always have to state to people, "Oh, yes, it will freeze twice. Just let it do its thing, and it will pass".

I do have the most updated form of software for both particular webcams that do the same thing. When I view others' webcams, I do not see the same problem, and two people I know who have one of the same models do not have a similar issue, either.

Could this signal a hardware/OS/networking problem? I have 100Mbps cable.

Also, of note, it is always with the same program --> Yahoo Messenger. Others do not have this same problem, it seems.

If it is always Yahoo, then, more likely than not it is a Yahoo thing...probably something to do with logging into the Yahoo servers and checking your mail, etc.

Make sure that your options when logging in don't include checking your mail.

Also, you may want to check the configuration of your firewall router to make sure that whatever port YM is using is actually getting through unhindered.

Should I forward whichever port? I've set no limitations upon it.

It's still happening, of course, and I'm not quite sure the check-mail aspect is what's causing it, as I've spoken to others who have that enabled as well and they had no such freezing problems.