WLHDD hanging after hdparm standby

Hi, I have a problem where my WLHDD is unresponsive after the hard drive goes into standby.

I use the command hdparm -S120 /dev/discs/disc0/disc to set the spin down time to 10 minutes. When I check the drive later it has stopped spinning. But next morning the drive is spinning. If I try to access the device either by web interface or ssh I get prompted for a password but never get a response. Holding down the power button to turn off does not work - I have to pull out the power plug to restart.

For a while I thought it was the logrotate cron job at midnight causing problems. But its not consistent, if I look at the log after a restart sometimes I can see that the cron jobs at midnight and 2AM have been logged, sometimes only the midnight job has been logged and sometimes even that job has not been logged. So its seems that the device is "hanging" at different times and not always after a specific event.

Sometimes if the hard drive is still in standby and I try to access the device I can hear the hard drive spin up but I cannot get a response from the device - have to pull the power plug again.

I don't know if the device is trying to do something before the hard drive is ready and gets stuck as a result - maybe it needs to "wait" a bit longer?

Also doesn't seems to happen when the hard drive has been in standby for short periods of time. If I issue the hdparm -y command to put the drive in standby or wait for the 10 minute spin down time to elapse and then access the device I hear the hard drive start up and I can get access.

I added a cron command to log the drive's power mode status every hour, using hparm -C and the device ran for a couple of days with out problems. It would spin down after 10 minutes, but it always spun up to write to the log file. I had been trying different combinations of the the hdparm settings for advanced power management and acoustic management and thought I had solved the problem. But once I took out the hourly cron jobs the problem reappeared. Its like it only happens once the drive has been asleep for a longer period of time. I wonder whether the drive is quietly slipping into a lower power mode after an elapsed standby time? Thats why I was playing around with APM settings.

I haven't got many ideas as to what might be the problem. The device is setup using wengi's olegs howto. Only difference is because its a 250 GB hard drive I have 4 partitions: 1-swap (512K), 2 /opt (1GB), 3 /temp/mnt/disc0_3 (100GB) and 4 /temp/mnt/disc0_4 (remaining space about 140GB).

Could the comparitively large size of the hard drive be a problem? or maybe the extra partition? Its a Western Digital 2500BEVE

It makes no difference if I issue the hdparm -S command to the whole disc (ie
hdparm -S120 /dev/discs/disc0/disc) or to each partition (hdparm -S120 /dev/discs/disc0/disc/part1 ... part2 etc).

Any suggestions of what to try next are most welcome.
Thanks,
Marty.