I'm having the same issue, Mountain Lion (10.8.2) address book, no settings have changed on my mac, but now the address book has vanished, watching the logs on the server, it never tries to access the personal address book, just looks at the groups and then stops. No error messages present.

Try to delete and re-add the account from Contacts.app.

Delete and re-add makes no difference:

sogo.log says:

127.0.0.1 - - [20/Nov/2012:16:42:39 GMT] "OPTIONS /SOGo/dav/myaccount/ HTTP/1.1" 401 0/0 0.011 - - 0
127.0.0.1 - - [20/Nov/2012:16:42:39 GMT] "OPTIONS /SOGo/dav/myaccount/ HTTP/1.1" 200 0/0 0.009 - - 0
127.0.0.1 - - [20/Nov/2012:16:42:39 GMT] "PROPFIND /SOGo/dav/myaccount/ HTTP/1.1" 207 521/439 0.010 1607 67% 0
127.0.0.1 - - [20/Nov/2012:16:42:40 GMT] "OPTIONS /SOGo/dav/myaccount/ HTTP/1.1" 200 0/0 0.004 - - 0
127.0.0.1 - - [20/Nov/2012:16:42:40 GMT] "PROPFIND /SOGo/dav/myaccount/Contacts/ HTTP/1.1" 207 710/717 0.075 5114 86% 0
127.0.0.1 - - [20/Nov/2012:16:42:40 GMT] "PROPFIND /SOGo/dav/myaccount/Contacts/groups/ HTTP/1.1" 207 508/717 0.012 1364 62% 0
127.0.0.1 - - [20/Nov/2012:16:42:40 GMT] "PROPFIND /SOGo/dav/myaccount/Contacts/groups/ HTTP/1.1" 207 285/181 0.008 - - 0
127.0.0.1 - - [20/Nov/2012:16:42:40 GMT] "PROPFIND /SOGo/dav/myaccount/Contacts/groups/ HTTP/1.1" 207 353/121 0.065 1902 81% 0
127.0.0.1 - - [20/Nov/2012:16:43:10 GMT] "PUT /SOGo/dav/myaccount/Contacts/groups/1c33d9a2-f72a-4b08-8b2b-5b8d91ceb5d8.vcf HTTP/1.1" 401 0/169 0.004 - - 0
127.0.0.1 - - [20/Nov/2012:16:43:11 GMT] "PUT /SOGo/dav/myaccount/Contacts/groups/1c33d9a2-f72a-4b08-8b2b-5b8d91ceb5d8.vcf HTTP/1.1" 404 208/169 0.009 - - 0
127.0.0.1 - - [20/Nov/2012:16:43:11 GMT] "PROPFIND /SOGo/dav/myaccount/Contacts/groups/ HTTP/1.1" 401 0/181 0.003 - - 0
127.0.0.1 - - [20/Nov/2012:16:43:11 GMT] "PROPFIND /SOGo/dav/myaccount/Contacts/groups/ HTTP/1.1" 207 285/181 0.007 - - 0
127.0.0.1 - - [20/Nov/2012:16:43:11 GMT] "PROPFIND /SOGo/dav/myaccount/Contacts/groups/ HTTP/1.1" 207 353/121 0.059 1902 81% 0
127.0.0.1 - - [20/Nov/2012:16:43:11 GMT] "PUT /SOGo/dav/myaccount/Contacts/groups/1c33d9a2-f72a-4b08-8b2b-5b8d91ceb5d8.vcf HTTP/1.1" 404 208/169 0.008 - - 0
127.0.0.1 - - [20/Nov/2012:16:43:11 GMT] "PROPFIND /SOGo/dav/myaccount/Contacts/groups/ HTTP/1.1" 207 285/181 0.008 - - 0
127.0.0.1 - - [20/Nov/2012:16:43:11 GMT] "PROPFIND /SOGo/dav/myaccount/Contacts/groups/ HTTP/1.1" 207 353/121 0.058 1902 81% 0

Contacts.app finds the account, but will only show the server groups and doesn't let me create new entries.

See the "404" error as sogo tries to "PUT" the entry

Have deleted and re-added the account, no change. Will grab sogo log and see if I've got the same 404 error as above.

Seems I have found a solution for MY setup (CentOS 5.8, SME Server):

for some reason, Apple contacts.app is not able to discover the default address book from SOGO any more. As soon as I create an additional address book via the SOGO frontend, the contacts.app under OS X discovers the newly created address book properly and works as expected.

Though under iOS, both address books are shown - which doesn't bother me much...

So you might give that a try as a SOGO user. - if the SOGO devs find the reason for this behavior I'd be grateful.

No joy on that with my system, also running on SME Server - logs as follows

127.0.0.1 - - [03/Dec/2012:19:25:41 GMT] "OPTIONS /SOGo/dav/cxbell/ HTTP/1.1" 401 0/0 0.001 - - 0
127.0.0.1 - - [03/Dec/2012:19:25:41 GMT] "OPTIONS /SOGo/dav/cxbell/ HTTP/1.1" 200 0/0 0.001 - - 0
127.0.0.1 - - [03/Dec/2012:19:25:42 GMT] "PROPFIND /SOGo/dav/cxbell/ HTTP/1.1" 207 510/439 0.003 1541 66% 0
127.0.0.1 - - [03/Dec/2012:19:25:42 GMT] "OPTIONS /SOGo/dav/cxbell/ HTTP/1.1" 200 0/0 0.001 - - 0
127.0.0.1 - - [03/Dec/2012:19:25:42 GMT] "PROPFIND /SOGo/dav/cxbell/Contacts/ HTTP/1.1" 207 755/717 0.005 6557 88% 0
127.0.0.1 - - [03/Dec/2012:19:25:42 GMT] "PROPFIND /SOGo/dav/cxbell/Contacts/groups/ HTTP/1.1" 207 503/717 0.002 1357 62% 0
127.0.0.1 - - [03/Dec/2012:19:25:42 GMT] "PROPFIND /SOGo/dav/cxbell/Contacts/4692-50B8DD80-5-1178B220/ HTTP/1.1" 207 321/181 0.002 - - 0

I can confirm this bug here on Ubuntu 12.04 with SOGo 2.0.3a

The personal addressbook no longer is discovered. Just the directory addressbook.

No changes on client side. Just SOGo upgrade from 2.0.2a to 2.0.3a

I uploaded my sogo.log with full debug enabled. Hope that helps

for some reason, Apple contacts.app is not able to discover the default address book from SOGO any
more. As soon as I create an additional address book via the SOGO frontend, the contacts.app under OS > X discovers the newly created address book properly and works as expected.

I tested this, too. And I can confirm it.

If creating a new address book, "directory0" - the LDAP address book - disappears and the newly created one is shown. But for me this is not a workaround, as I have this bug on several SOGo servers :(

Fixed. See https://github.com/inverse-inc/sogo/commit/5667bb1b11a7f80dbc4d72deab1f86d8ea30d75e

Notice: with OS X, SOGo only returns the personal addressbook along with the first shared source. However, you can control which of your shared sources is returned since the list is now sorted first.