After a year working with DotNetNuke, I attempted to use Admin > Site Log today for the very first time (DNN 4.5.4). I experienced all the same problems mentioned in this thread (and other threads). Since I am new to this issue, I tried to take a fresh approach. Here is what I found worked for me to resolve the error message: 'Your Hosting Provider Has Disabled the Site Log History Feature For Your Portal.'
Login as Host
Host > Host Settings > Advanced Settings > Other Settings
Site Log Storage: (x) Database
Site Log Buffer (Items): 1
Set Site Log History (Days): 45 (or some other value, probably 30 days or more)
Update
Admin > Site Settings > Advanced Settings > Host Settings
Site Log History (Days): 45 (or whatever value you entered above)
Update
Host > Schedule
Edit: DotNetNuke.Services.Log.SiteLog.PurgeSiteLog, DOTNETNUKE
Schedule Enabled: [x] Yes
Update
Host > Host Settings
Restart Application (bottom of page)
Now, when returning to Admin > Site Log - you should see a message like:
Your Hosting Provider Has Limited Your Portal To 45 Days Of Site Log History.
Pick a report. For my first report I selected 'Page Popularity' > Display
... and there I was able to see web/portal statistics, without error. 
Note: I saw a post that said 'Site Log History (Days): 0 = Unlimited'. I thought '0' = disabled. If 0 = Unlimited, the most important step above would be to enable the Host > Schedule job named 'DotNetNuke.Services.Log.SiteLog.PurgeSiteLog, DOTNETNUKE'.
I think it's better not to collect Site Log statistics forever - unlimited - even if that is what 0 means.