Cryptic authorization dialog won't go away

[Guest]

I have been using Kubuntu for a little over a year, and recently upgraded to 10.04. The (attached) authorization dialog is asking me to supply a username and password to access a site, but the site is listed as "your valid user account or api key". If I choose cancel, the message just pops up again in a few minutes.

Does anyone know how to find out what is generating this message, and ultimately how to get rid of it? It is not asking for my username and password as I have already tried that. My best guess is that it has something to do with apikeys, but that is beyond my expertise. The keys I am have added are pasted below in case that is helpful.

sudo apt-key list
[sudo] password for slaughjc:
/etc/apt/trusted.gpg
--------------------
pub 1024D/437D05B5 2004-09-12
uid Ubuntu Archive Automatic Signing Key <ftpmaster@ubuntu.com>
sub 2048g/79164387 2004-09-12

pub 1024D/FBB75451 2004-12-30
uid Ubuntu CD Image Automatic Signing Key <cdimage@ubuntu.com>

pub 1024D/E2A11821 2007-03-06
uid Vincent Goulet <vincent.goulet@act.ulaval.ca>
sub 2048g/6071645B 2007-03-06

pub 1024D/6DFBCBAE 2008-07-14
uid Sun Microsystems, Inc. (xVM VirtualBox archive signing key) <info@virtualbox.org>
sub 2048g/78A86EAF 2008-07-14

pub 1024D/98AB5139 2010-05-18
uid Oracle Corporation (VirtualBox archive signing key) <info@virtualbox.org>
sub 2048g/281DDC4B 2010-05-18