In the past, i had the first message often.
I’ve send an email to my host (QuébecIT), and it said something in the config of files had to be fixed.
He also added that i just have to tell him if it ever happen again.
For the other problem, i think it’s just partially related.
I mean, your host doesn’t seems to like when people are using softwares on theirs sites.
Maybe they could have blocked a very used wiki or forum too.
Or even a blog like dotclear.
Before installing a software on our hosting, it’s not a bad idea to ask them what they think of it and it’s impact on the others sites on the shared hosting.
But, in the end, maybe your host is not a good one, or the “forfait” (sorry, my first language is french) you selected was not the good one.
Oh, and i’m sorry but i dont think the devs can really help here since it’s not a Piwik problem.
But could it be a misconfiguration problem ?
Rereading your first post, i think that the usage your doing of Piwik (50.000 visitors) really need a good professionnal and costly hosting. Even my hosting woudn’t be able to handle that.