Too many banned emails cause error

When I add a lot of banned emails (2,000), I get the
following error:

Bug in Mailman version 2.1.5

We're sorry, we hit a bug!

If you would like to help us identify the problem,
please email a copy of this page to the webmaster for
this site with a description of what happened. Thanks!
Traceback:

Traceback (most recent call last):
File "/var/lib/mailman/scripts/driver", line 96, in
run_main
main()
File "/usr/lib/mailman/Mailman/Cgi/admin.py", line
175, in main
change_options(mlist, category, subcat, cgidata, doc)
File "/usr/lib/mailman/Mailman/Cgi/admin.py", line
1296, in change_options
gui.handleForm(mlist, category, subcat, cgidata, doc)
File "/var/lib/mailman/Mailman/Gui/Privacy.py", line
510, in handleForm
GUIBase.handleForm(self, mlist, category, subcat,
cgidata, doc)
File "/var/lib/mailman/Mailman/Gui/GUIBase.py", line
158, in handleForm
doc.addError(
File "/var/lib/mailman/Mailman/htmlformat.py", line
341, in addError
self.AddItem(Header(3, Bold(FontAttr(
TypeError: not enough arguments for format string

Python information:

Variable Value
sys.version 2.3.4 (#2, Dec 3 2004, 13:53:17) [GCC 3.3.5
(Debian 1:3.3.5-2)]
sys.executable /usr/bin/python
sys.prefix /usr
sys.exec_prefix /usr
sys.path /usr
sys.platform linux2

Environment variables:

Variable Value
HTTP_COOKIE
juviejustice+admin=2802000000698c6be441732800000033643636393736363938333663663931393038626136396563336235316637303261316364303166;
support+admin=2802000000696f6de441732800000031313539613635393437653164613231303763393137306339363466643362393432666432396263
SERVER_SOFTWARE Apache/2.0.52 (Debian GNU/Linux)
PHP/4.3.10-2 mod_ssl/2.0.52 OpenSSL/0.9.7e
SCRIPT_NAME /mailman/admin
SERVER_SIGNATURE
REQUEST_METHOD POST
HTTP_KEEP_ALIVE 300
SERVER_PROTOCOL HTTP/1.1
QUERY_STRING
CONTENT_LENGTH 74313
HTTP_ACCEPT_CHARSET ISO-8859-1,utf-8;q=0.7,*;q=0.7
HTTP_USER_AGENT Mozilla/5.0 (X11; U; Linux i686;
en-US; rv:1.7.5) Gecko/20041128 Firefox/1.0 (Debian
package 1.0-4)
HTTP_CONNECTION keep-alive
HTTP_REFERER
https://xxx.xxx.xxx/mailman/admin/juviejustice/privacy/subscribing
SERVER_NAME xxxx.xxxx.xxxx
REMOTE_ADDR xxx.xxx.xxx.xxx
PATH_TRANSLATED
/srv/virtual_web/secure.mediajumpstart.net/public_html/juviejustice/privacy/subscribing
SERVER_PORT 443
SERVER_ADDR 10.0.0.163
DOCUMENT_ROOT /srv/virtual_web/xxx.xxx.xxx/public_html
PYTHONPATH /var/lib/mailman
SCRIPT_FILENAME /usr/lib/cgi-bin/mailman/admin
SERVER_ADMIN apache@xxxx.xxx
HTTP_HOST xxx.xxx.xxx
HTTPS on
REQUEST_URI
/mailman/admin/juviejustice/privacy/subscribing
HTTP_ACCEPT
text/xml,application/xml,application/xhtml+xml,text/html;q=0.9,text/plain;q=0.8,image/png,*/*;q=0.5
GATEWAY_INTERFACE CGI/1.1
REMOTE_PORT 33792
HTTP_ACCEPT_LANGUAGE en-us,en;q=0.5
CONTENT_TYPE application/x-www-form-urlencoded
HTTP_ACCEPT_ENCODING gzip,deflate
PATH_INFO /juviejustice/privacy/subscribing