Several months ago I started using the Google Contacts add-on for Thunderbird and it’s been hanging periodically ever since. I just thought it’s Thunderbird and tried all those compacting folder, resetting the cache thing.
Today it hang again and I was frustrated, so I did
dtruss (strace) on it and found that it seemed to be stuck in an infinite loop trying to access my Google contact feed.
I replaced it with the gContactSync add-on and it’s working smoothly now.