Multiple errors when running full file backup

I have just setup urbackup server on my windows server 2008 FS. I have created a share that everyone and domain users have access to. I have mapped the share on the machine, and added that share as a backup path, but when i try and run a full image backup i get the following errors;

Starting full file backup…
backupcom->AddToSnapshotSet(volume_path, GUID_NULL, &dir->ref->ssetid) failed: EC=VSS_E_VOLUME_NOT_SUPPORTED
Creating shadowcopy of “backups” failed in indexDirs().
Cannot access directory to backup: “\bsr-serv-1\backups:”
Constructing of filelist of “Steve” failed: error - index error
Backup had errors. Deleting partial backup.
Exponential backoff: Waiting at least 40m before next file backup