CreateSnapshot failed, vmRef "48"

[rowdy]

One day it was running fine, the next it wasn't.
I'm getting this error with version 4.0 and 4.1.2 (I updated Veeam to see if it would help).
I'm using an (paid) ESXi 4.0 as a host (without vSphere server).
I have more (different) tasks running on the same (esxi) server, they are still running fine and making backups as they should.
It appears that for this particular server, VeeAm can't make a snapshot anymore.

Also, I have 2 VM is the backup JOB that's failing. On some days, one VM is backup up (success) and the other one states (failed).
On other days, it only shows the failed one.
Screenshot:


Haven't yet tried anything to resolve this, because I don't want to risk trying anything that might make it worse.
There is currently no snapshot present on the involved VM.

Any help or suggestions would be greatly appreciated.
(I am posting here because I don't really believe this to be a Veeam issue, but rather a VMWare issue but I'm not sure)



**VeeAm shows this:**
0 of 0 files processed

Total VM size: 145,00 GB
Processed size: 0,00 KB
Processing rate: 0 KB/s
Backup mode: NBD without changed block tracking
Start time: 3-8-2010 3:47:23
End time: 3-8-2010 3:53:26
Duration: 0:06:03

Enabling changed block tracking...
Changed block tracking cannot be enabled: virtual hardware version 7 or later required.

Creating snapshot
CreateSnapshot failed, vmRef "48", timeout "1800000", snName "VEEAM BACKUP TEMPORARY SNAPSHOT", snDescription "Please do not delete this snapshot. It is being used by Veeam Backup.", memory "False", quiesce "False"
The operation is not allowed in the current state.

*************Sometimes it also shows this:********************
0 of 0 files processed

Total VM size: 145,00 GB
Processed size: 0,00 KB
Processing rate: 0 KB/s
Backup mode: NBD without changed block tracking
Start time: 11-8-2010 3:22:06
End time: 11-8-2010 3:23:11
Duration: 0:01:04

Enabling changed block tracking...
Changed block tracking cannot be enabled: virtual hardware version 7 or later required.

Creating snapshot
CreateSnapshot failed, vmRef "48", timeout "1800000", snName "VEEAM BACKUP TEMPORARY SNAPSHOT", snDescription "Please do not delete this snapshot. It is being used by Veeam Backup.", memory "False", quiesce "False"
Failed to login to "172.18.0.31" by SOAP, port 443, user "root", proxy srv: port:0
The remote server returned an error: (503) Server Unavailable.

[Gostev]

Hello Rowdy, I think it would be best to seek VMware support assistance with this, and have them review vCenter and ESX logs (these should definitely provide more insight on what is not working).

If needed, our support will be able to instruct you how to create snapshot through VMware API manually (via managed objects browser) - this would be the exact same VMware API command Veeam Backup uses to create snapshot. This would allow you to reproduce and demonstrate the issue to VMware support w/out Veeam Backup involved (if this becomes necessary).

[rowdy]

I also noticed the 'take snapshot' and 'edit settings' amongst others are grayed out in VPX Client for this particular VM...
This is really odd...

I will try the 'reboot it all' fix first tonight.

[rowdy]

'reboot it all' fixed it once more...