Comment 132 for bug 633352

I've just been able to solve the issues I had of:
- not being able to dismiss/snooze the alarms of my appointments
- Lightning not synchronizing with the calDAV server (Radicale) I use to cloudlessly sync my
  calendars between my notebook PC and Android smartphone.

In the faulty setup I had Thunderbird and Lightning were both installed from the repositories.
I've solved the issues as follows:

0 - In Thunderbird, open the Properties of each of your calendars and write down their locations
    (just in case you need them later ...)
1 - Close Thunderbird
2 - Uninstall Lightning package (xul-ext-lightning), using the package management tool or
    the CLI typing "apt-get uninstall xul-ext-lightning"
3 - Re-start Thunderbird, now running without Lightning calendar extension
4 - Install Lightning as an extension from inside Thunderbird:
    go to Tools->Add-ons->Extensions, search for "lightning" and then install it.
    If prompted, re-start Thunderbird
5 - Check that your calendar(s) are correctly set and if need be edit/add them using your notes
    as taken at previous point "0"

Now everything seems to run flawlessly.

I can just be grateful to all people writing on this post, especially Ed, as I alone would not been able to understand that "finger points to Thunderbird/Lightning" as clearlly stated three comments up from here.
Hope this might be of help to someone out there desperately struggling to solve all this, like I've being doing during the whole last week while my calendars were unreliable and unusable.

Lenovo Thinkpad T510
 Linux Mint 18 Sarah 64bit [Ubuntu 16.04]
 Mate 1.14.1
 Thunderbird 45.5.1
 Lightning 45.5.1, then Lightning extension 4.7.4
 Radicale 1.1.1

Samsung Galaxy SIII (GT-I9300)
 Android 4.3
 DAVdroid 1.3.4.1-ose (installed with F-Droid app from f-droid.org repository)