Space has been allocated on //server/Mac/Backup but every time I click Start under Backup Disk Status, I get an error "Could not complete the operation, Please retry later, or manually if possible, or after system reboot. If the problem persists reinstall the software."

Any suggestions?

This should probably be moved to the Mac forum. Did you create the Time Machine volume from within the HP MSS control panel? Was that successful? How big of a TM volume did you create and how much space is available on your system?

Did you try what is suggested: after reboot, after reinstall? Did you try to review the logs in Console.app about some HP related records?

Did you reboot the Mac as well as the HP? I just set up an EX490 yesterday, and the Time Machine volume didn't show up on the mac until I did that. However, immediately after rebooting my MacBook and logging in, there was an HP MediaSmart Backup volume mounted on my desktop and my mac asked me if I wanted to use that volume for Time Machine.

If you're not already doing it, I would highly suggest using a wired ethernet connection. I had mine going off on my 802.11g network and was getting about 500-700 KB/s, which isn't too bad, but almost as soon as I plugged into my ethernet hub, the speed went up by a factor of more than 10 to 7-9 MB/s.

It backed up over 200 GB overnight.

I'm now having the same problem. How do I get around this?

1) I cannot create a new Backup disk.
2) I cannot access an existing Backup disk any more, it used to work.

Is there anything related in logs on Mac & on the server?

Check the version of your MSS and check for updates on the HP software on the Mac.

I think we are seeing a rash of people complaining about this because their HP automatically updated to the new 3.0.1 service pack but they have not updated the HP clients on their Macs.

Actually, as I observe, there is a Software Update section in the Mac software preferences, which reports about updates if any present.