event can't be cancelled Noté 3 sur 5 étoiles

don't know where to report bug... so here it is:
- sometimes (don't know which action does that) an event cannot be cancelled. Once the alert comes up, deactivate the alert button does not work (almost as if inactive). You have then the popup ad vidtam eternam... which is long and very annoying. Only way I found: save the calendar. Remove it. Reinstall the calendar. 99% of the events can be cancelled or moved, though...
Only happens since 1.9 version apparently.
I am using a deported agenda using Zimbra
Best Philippe

Cette critique concerne une version précédente du module (1.9). 

I can imagine this is the mItemInfoCache bug, please check your error console for related messages. This bug is known, but I can't reliably reproduce it. The workaround you found is the only way to get rid of this issue right now.

I would have appreciated you would have taken the little time to google for "mozilla calendar file bug", which would have lead you directly to our issue tracker, there are bugs filed for your issue.