USB hard drive no longer mounting

[cliverlong]

Software
XBian version: 1.0 Beta 2
XBMC version: Gotham 13.0
Overclock settings: Default

Hardware
Power supply rating: 1.5 A
RPi model (model A/B 256mb/512mb): B 512Mb
SD card size and make/type:Sandisk 8GB
Network (wireless or LAN): Ethernet LAN
Connected devices (TV, USB, network storage, etc.): TV HDMI, powered USB hub with keyboard and occasionally hard disk to hub

Logfile
Link to logfile(s): https://dl.dropboxusercontent.com/u/32576758/2014-07-13-Xbian-debug-log-connect-disk.txt

Problem description:

Hello,

I have been using a 250GB laptop hard drive in a USB caddy to "serve" video files to the Rpi/xbian and this has worked well. I have the automount setting on in the configuration (confluence> Settings) and until recently the disk mounted within a second or so and was visible under xbmc "videos" or "file manager". I could then select any of the video files on the device and it would start playing without stuttering. In the past week the device is no longer visible when connected to the rpi. I have plugged the disk into the usb port of two different laptops running Windows 8.1 and the disk mounts within a few seconds and various video files play without error under media player or VLC.

I haven't purposely changed any setting or upgraded any software on the raspberry pi but maybe something has updated in the "background"? I could just reinstall xbian but I would appreciate any suggestions on how to fix this without going that far. I have attached to this post a public link to a xbian log file. I can't see any log file entries that suggest a sub drive has been detected. I have looked at the system settings when the usb disk is plugged into the rpi and I think the only detected device is the SD Card. However, my technical knowledge is limited so I may be missing something. I can ssh into this rpi so I can run any diagnostic commands anyone suggests.

How to reproduce:

Plug the disk in and unplug any number of times, via the hub. The hub works fine as that is how the drive was attached in the past and remains the "route" to attach the keyboard to the rpi. If I try to plug the usb dsk directly into the rpi it causes the device to crash - I guess from drawing too much power.

Regards,