Hi, I was receiving a storage engine error yesterday so after reading a few similar posts here I contacted my host.
They cleared the cache and I was able to see my table report again however since then piwik is not collecting data for any of my sites. I’ve checked “piwik_log_visit” and can see there also there is no data since yesterday.
Can anyone help at all? My knowledge is basic so please speak slowly! 
Thanks.
My chat log with HostGator re: this same problem:
(9:11:06pm)Jonatan B.:I am seeing that there is a security rule being hit by the software I can clear this out for you if you wish me to.
(9:11:27pm)Phillip Crum:Explain it to me in English, please. Slowly.
(9:12:02pm)Jonatan B.:Its no problem
(9:12:26pm)Jonatan B.:It seems that the software Piwik is trying to do something that is consider unsafe, by default, but we all know its not so we can clear out this warning
(9:12:36pm)Jonatan B.:Kind of like a false positive on your Antivirus.
(9:12:55pm)Phillip Crum:Why all of a sudden? New setting last nite?
(9:13:59pm)Jonatan B.:No, they can be hit by any number of reasons and then they get blocked until cleared.
(9:14:26pm)Phillip Crum:Funny that many others are having the same problem simultaneously??
(9:14:41pm)Phillip Crum:How do I keep this from happening again?
(9:17:15pm)Jonatan B.:All we have to do is whitelisted and that will take care of it.
Did they clear it and did that resolve the issue?
Just had reply from hostgator saying they have whitelisted the ModSecurity rule.
Checked stats and all is well again!
Thanks for the info Altstatten!