Lightning 0.8 and external calendars not working properly

Hello,

I updated from Lightning 0.7 to 0.8. I use several different external
calendars. These are:

- An .ics file on a Webdav resource
- A CalDAV calendar (on a Kerio mail server), read-only
- A custom solution to read calendar entries from Microsoft Exchange.
This is a Perl script on a local tomcat that returns an .ics file.
This is again read-only.

When the calendar is changed externally (so not by Thunderbird/
Lightning, but by an external program, e.g. Kerio web access or
Outlook Web access), the changes were reflected in Lightning before
(at least after calling 'reload external calendars').

After updating to 0.8, this still works for the first calendar (ics on
a Webdav resource), but it does not work for the other two calendars.

If I add a new appointment, Lightning does not show it. But it still
shows the old entries that were present before I updated to 0.8. Even
if I call 'reload external calendars' or I restart Thunderbird, it
only shows the old entries, but does not show the new ones.

Is this a bug in 0.8? Or what do I do wrong?