After applying patch 1 for 6.1.0.181 you are no longer able to backup or replicate Hyper-V virtual machines, jobs fail with the "Unknown drive type [ISO]" error. The following entries can be seen in the job log:
[timestamp] <01> Error Failed to parse drive xmlnode. Xml: [<drive0><pathname type="string">C:\Users\administrator\Downloads\name.ISO</pathname><type type="string">ISO</type></drive0>] at Veeam.Backup.Common.CExceptionUtil.RegenTraceExc(Exception originalExc, String formatString, Object[] args)
[timestamp] <01> Error at Veeam.Backup.Core.CHvVmConfigFile.ParseDrive(XmlNode node)
[timestamp] <01> Error at Veeam.Backup.Core.CHvVmConfigFile.ParseController(XmlNode node, Int32 controllerNum)
[timestamp] <01> Error Unknown drive type [ISO] at Veeam.Backup.Core.CHVVMCfgDrive.ConvertStringToType(String typeStr)