@mbrsolution To be precise, it's not an error, it's a warning:
[05-May-2013 16:59:33] WARNING: File "/home/[..]/stats/logs" is not readable!
So it says right there: not readable. That's all the warning is about, and as it is a only a warning, not an error it doesn’t stop the running process (your backup) from being completed.
The second warning looks a bit different, it says:
[05-May-2013 16:59:33] WARNING: Link "/home/[..]/stats/error_logs" not followed.
error_logs seems to be a link (most likely an alias for another directory in this case) which BackWPup does not follow. That's correct behavior, because otherwise everything in that directory would be included in the process.
BackWPup, or PHP actually, is simply saying: “Hey, you wanted me to do this and that, but I can only do this, not that, and I thought I’d better let you know.”