Steps to reproduce:
1. Start Evolution
2. Navigate to Calendar Tab
3. Import webcal://30boxes.com/iCalUser/1542741/SpencerWohlers/0460f7b06e09b93cd9bf1698f2a39fc9/0/


Stack trace:
System: Linux 2.6.20-16-generic #2 SMP Fri Aug 31 00:55:27 UTC 2007 i686
X Vendor: The X.Org Foundation
X Vendor Release: 70200000
Selinux: No
Accessibility: Disabled
GTK+ Theme: Clearlooks
Icon Theme: UbuntuStudio

Memory status: size: 1757184 vsize: 1757184 resident: 491520 share: 421888 rss: 491520 rss_rlim: 4294967295
CPU usage: start_time: 1189102376 rtime: 0 utime: 0 stime: 0 cutime:0 cstime: 0 timeout: 0 it_real_value: 0 frequency: 100

Backtrace was generated from '/usr/libexec/evolution-data-server-1.10'

(no debugging symbols found)
Using host libthread_db library "/lib/tls/i686/cmov/libthread_db.so.1".
(no debugging symbols found)
(no debugging symbols found)
(no debugging symbols found)
0xffffe410 in __kernel_vsyscall ()

+ Trace 160946

----------- .xsession-errors ---------------------
(avant-window-navigator:6944): Wnck-WARNING **: Unhandled action type (nil)
(avant-window-navigator:6944): Wnck-WARNING **: Unhandled action type (nil)
(avant-window-navigator:6944): Wnck-WARNING **: Unhandled action type (nil)
(avant-window-navigator:6944): Wnck-WARNING **: Unhandled action type (nil)
(avant-window-navigator:6944): Wnck-WARNING **: Unhandled action type (nil)
calendar-gui-Message: Check if default client matches (1186556817.28156.7@feistyfical 1189101559.13825.4@feistyfical)
(avant-window-navigator:6944): Wnck-WARNING **: Unhandled action type (nil)
(avant-window-navigator:6944): Wnck-WARNING **: Unhandled action type (nil)
--------------------------------------------------

Other information:
I can import my calendar from Google Calendar just fine, but not my 30Boxes calendar. A calendar import of my 30Boxes calendar into Lightning produces a timezone error, but import into Google Calendar of my 30Boxes calendar goes fine and an iCalendar validator says it checks out fine:

http://severinghaus.org/projects/icv/?url=30boxes.com%2FiCalUser%2F1542741%2FSpencerWohlers%2F0460f7b06e09b93cd9bf1698f2a39fc9%2F0%2F