General :: Unable To Use Popup Menu When Selecting Text?

I've been using Linux for about six years now, and I joined this website hoping to learn more about Linux, keep updated with Linux news, others less experienced than me; I spend so much time on Reddit I rarely remember there's a whole Internet how there and I've yet to really visit this website since I registered. I'm posting this in the newbie section because the problem I'm having feels like it probably has a simple solution, but I don't what to do. If this forum is inappropriate, I suppose a mod could move it?

Anyway, upon highlighting a link in either Firefox 4 nightly or Chromium, I get this pop-up menu: [URL](copy paste and remove the space between the h and the t - and yes, this is a "screenshot" taken with a camera, as this menu seems to inhibit the functioning of the PrintScreen key for some reason) I do not need to click - as soon as a URL is highlighted, the menu pops up, forcing me to click away in order to cancel the menu. At first I assumed it was a Firefox thing - it happens in both 3.6 and 4 Nightly - so I began checking all of my add-ons (only 4) and plugins to see if I have some plugin causing this. Nothing seemed to be.

When I switched to Chromium, I quickly realized the same thing happens in Chromium, as well, so it's independent of what browser I'm using. This leads me to believe it's some package I have installed (apt-get, I'm using Linux Mint on this laptop, and on my other computers, which are running Arch, I do not encounter this in either Chromium or Firefox4) that's causing this, so if someone could just identify what package it is I can remove it. Or maybe my assumption is incorrect and there's something else that leads to this popup, but either way, it's really annoying and I want it gone!