Some of this information was already provided in the original post, but here goes:

1) Windows 7 Home Premium 64-bit with AVG Free and Verizon FIOS
2) I attached an exact screenshot of the error message.
3) Often. I'd say multiple times a day.
4) It happens in any area: cities, field, wards, and dungeons
5) I've been running around, on choco, in mid-fight, and even just standing there or /sitting
6) I've been both solo and in party. Have had up to three others in party with me, usually less.
7) No way to know this. In the screenshot I attached, there was only two. In towns, considerably more.
8) When I click Okay in the screenshot, I'm kicked to character selection screen. I cannot immediately log back in; I believe the game thinks I am still logged in. If I back out to the title screen and wait about 30 seconds, I can then proceed forward to the character screen and then choose it to log back online.

If there's any other info I can provide, just let me know.