Hello,
for testing purposes I installed vRanger 5.5 within a VM and deployed a VA (v 1.5) associated to the cluster. The two hosts in this cluster are running ESXi 5.0.0; the VC Server is v5.0.0 too. Backups via HotAdd/LAN configured to run on the vRanger VM work nicely, but if I try to use the VA instead, there is always the same error:
[2012-07-05 14:21:05.370]: vRanger Backup & Replication - v5.5.0.25454
[2012-07-05 14:21:05.386]: Selected Options: Backup powered on machines only. | Check destination for free space. | Compress backed up files. | Update notes with the latest backup results. | Selected SpaceSavingTech: None | Included Disks [13, 27, 14, 21, 55, 29, 40, 23, 34, 32, 46, 24, 49, 44, 56, 37, 51, 18, 25, 26, 10, 8, 58, 60, 22, 28, 9, 64, 53, 59, 50, 62, 16, 17, 57, 1, 52, 45, 19, 31, 4, 47, 20, 63, 43, 12, 42, 2, 39, 30, 15, 5, 35, 36, 33, 54, 48, 3, 61, 11, 41, 38, 6, 7].
[2012-07-05 14:21:05.386]: Task for virtual machine w7_tools was queued.
[2012-07-05 14:21:15.854]: SourceVm:w7_tools | Uuid:420c02a6-8727-c395-9d59-db4269103981 | VC:192.168.66.17, Host:esxi6sc2.syslog.local [ESXi 5.0.0]
[2012-07-05 14:21:15.854]: Beginning backup task for w7_tools
[2012-07-05 14:21:15.870]: Starting task validation.
[2012-07-05 14:21:15.870]: Connection to esxi6sc2.syslog.local was properly validated.
[2012-07-05 14:21:15.870]: esxi6sc2.syslog.local is properly licensed.
[2012-07-05 14:21:15.886]: Test connection to repository esxi_test starting...
[2012-07-05 14:21:17.214]: Test connection to repository esxi_test successful!
[2012-07-05 14:21:17.698]: Ending task validation... success!
[2012-07-05 14:21:17.698]: Beginning initialization of backup information.
[2012-07-05 14:21:17.698]: Retrieving the tasks parent information.
[2012-07-05 14:21:18.042]: Retrieving save points for any full backups associated with this job.
[2012-07-05 14:21:18.573]: Finished initialization of backup information successfully.
[2012-07-05 14:21:18.573]: A Full backup will be run for this task.
[2012-07-05 14:21:18.792]: Gathering credentials for w7_tools completed.
[2012-07-05 14:21:19.089]: Checking for VMotion completed.
[2012-07-05 14:21:20.401]: Gathering data for w7_tools from API completed.
[2012-07-05 14:21:21.870]: Gathering data for esxi6sc2.syslog.local from API completed.
[2012-07-05 14:21:22.651]: Retrieving the VM BIOS configuration completed.
[2012-07-05 14:21:23.511]: Gathering credentials for ha5-vRangerVA completed.
[2012-07-05 14:21:24.292]: Gathering data for ha5-vRangerVA from API completed.
[2012-07-05 14:21:25.245]: Validating connectivity to virtual appliance 192.168.66.233 completed.
[2012-07-05 14:21:28.776]: Checking free space on esxi_test completed.
[2012-07-05 14:21:31.964]: Creating a snapshot for vRanger completed.
[2012-07-05 14:21:33.479]: Gathering data for w7_tools from API completed.
[2012-07-05 14:21:33.604]: Local machine is a virtual machine.
[2012-07-05 14:21:33.745]: Backup task will attempt to use VA-based VDDK HotAdd.
[2012-07-05 14:21:34.933]: The change block filter failed on vix:r:192.168.66.17:902:[ams2100_0203_syslog2] w7_tools/w7_tools.vmdk.
[2012-07-05 14:21:40.979]: Backup failed: An internal error occurred during execution, please contact Quest support if the error persists. Error Message: 3201 - can't open [ams2100_0203_syslog2] w7_tools/w7_tools.vmdk
[2012-07-05 14:21:40.979]: The failed backup task will be retried.
[2012-07-05 14:21:49.323]: Backup failed: An internal error occurred during execution, please contact Quest support if the error persists. Error Message: 3201 - can't open [ams2100_0203_syslog2] w7_tools/w7_tools.vmdk
[2012-07-05 14:21:49.339]: The failed backup task will be retried.
[2012-07-05 14:22:03.573]: Backup task using VA-based VDDK HotAdd failed: An internal error occurred during execution, please contact Quest support if the error persists. Error Message: 3201 - can't open [ams2100_0203_syslog2] w7_tools/w7_tools.vmdk
[2012-07-05 14:22:03.589]: Check the manual for compatibility issues when attempting Lan-free operations.
[2012-07-05 14:22:03.589]: Backup task will be attempted using a VA-based VDDK network connection.
[2012-07-05 14:22:04.370]: The change block filter failed on vix:r:192.168.66.17:902:[ams2100_0203_syslog2] w7_tools/w7_tools.vmdk.
[2012-07-05 14:22:09.886]: Backup failed: An internal error occurred during execution, please contact Quest support if the error persists. Error Message: 3201 - can't open [ams2100_0203_syslog2] w7_tools/w7_tools.vmdk
[2012-07-05 14:22:09.886]: The failed backup task will be retried.
[2012-07-05 14:22:17.401]: Backup failed: An internal error occurred during execution, please contact Quest support if the error persists. Error Message: 3201 - can't open [ams2100_0203_syslog2] w7_tools/w7_tools.vmdk
[2012-07-05 14:22:17.417]: The failed backup task will be retried.
[2012-07-05 14:22:29.042]: Removing snapshot for vRanger completed.
[2012-07-05 14:22:31.323]: Backing up disk 'vix:r:192.168.66.17:902:[ams2100_0203_syslog2] w7_tools/w7_tools.vmdk:moref=vm-960:snapshot-3873:6' completed.
[2012-07-05 14:22:31.386]: An internal error occurred during execution, please contact Quest support if the error persists. Error Message: 3201 - can't open [ams2100_0203_syslog2] w7_tools/w7_tools.vmdk
I did a lot of checking and re-checking (DNS, credentials, network access etc.), but I can't figure out what, exactly, the problem might be.
Suggestions, anyone? 
Regards, Markus