I am having a very similar problem to this post which seems like it was never resolved.
http://forum.piwik.org/read.php?2,78139
Here is my api call
method=Actions.getDownload
&downloadUrl=$urlEncoded
&period=range
&date=2012-04-20,2012-04-25
&format=php
&token_auth=x
&idSite=1
I was able to get this to work in testing just fine, but now that the site has scaled up, I am either getting zero arrays or nonsense numbers.
The urlEncded is the location of a jpeg on the server.
In live view, I can see the downloads being recorded in the visit log, so I a completely annoyed that I can’t query this data correctly.
Any help would be greatly appreciated.