I upgraded to 2.2 fast – and some days later (at the end of april) the problems begins: The daily and weekly report works without any problems, but no data for the month. CoreConsole says (after about 8 minutes working after the daily/weekly reports, which only last 11.4 seconds for monday and the few hours of tuesday) - even after upgrading to 2.2.1 and trying again today:
INFO CoreConsole[2014-05-06 08:24:20]  ERROR: Got invalid response from API request: https://www.___.de/piwik/index.php?module=API&method=API.get&idSite=1&period=month&date=last9&format=php&token_auth=d046e15ee65d739356fadd03932cbaa8&trigger=archivephp. The response was empty. This usually means a server error. This solution to this error is generally to increase the value of ‘memory_limit’ in your php.ini file. Please check your Web server Error Log file for more details.
Increasing memory does not help. In syslog I found:
kernel: [6384318.127657] php5: segfault at 7f2ee5c68e68 ip 00000000006bddfd sp 00007fff7e3216f0 error 4 in php5[400000+6f4000]
I use pure Debian 7.5 (amd64).