This is a strange one, because I am unable to replicate it, but thankfully I do have a picture, so here goes.
Platform: Windows 7 x64
ISP: AT&T
Type of Internet Connection: FiOS
Internet Connection Speed: 1mbps upload / 6mbps download
Date & Time: October 22nd, ~11:30AM Central
Frequency: Only once
Character Name: Raldo Volca
Race: Hyuran
World: Selbina
Class + Level: MRD 50
Area and Coordinates: (44/45, 29)
Party or Solo: Solo
NPC Name: Vhaso Tayunn
Monster Name: N/A
In-Game Time: Around 05:00
I can't really give steps to replicate, because I wasn't able to replicate it. I don't know if that means the bug isn't worth mentioning, but I'll leave that up to someone else to decide. Here's a quick rundown of what I was doing shortly before it happened:
I just finished gathering all the quest items for "Freedom Isn't Free" and I was headed down toward Little Ala Mhigo to do a different quest when I passed by the little caves that the NPC Vhaso Tayuun stays in. Curious as to what she says, I went to talk to her, and right when I spoke with her, I got aggro from a nearby Antling Digger. I killed it and then spoke with Vhaso Tayuun. I got only a portion of her text in the box in the middle of the screen (but all of it in my log). I could still move the camera around, but nothing else, as if it was waiting for the rest of the text that just wasn't coming. I waited for about 1 minute, then terminated my wireless connection in order force a disconnection from the server. When I logged back on, I was able to speak with the NPC just fine without getting locked up--I even pulled another Antling Digger then spoke with her and it still didn't lock up, so I am complete baffled as to what caused this fluke issue. As a software developer, I know that bugs like this are often precursors to potentially larger issues, so I thought I'd go ahead and report it even though I was unable to replicate it myself.
Here is a picture I took before I forced my disconnection:
(I apologize if this breaks the forum width limits, but I figure it's best to give you the highest-quality image since I don't know what the problem is)
For anyone that notices: Please ignore the seemingly stupid gear choices. I was leveling my very-low-level Gladiator right before this and I didn't switch gear.