Mybook studio appears as unformatted since security update - Help!

I hope one of you guys can help me with my problem. I have an iMac running 10.6.2 and use a MyBook Studio 1GB connected via Firewire800 for my time machine backups and to store movies… on two partitions. All used to work fine until I installed the latest security update a few days ago.
Since then I can’t connect to the hard drive anymore. Whenever I boot my Mac I get the message that the disk I inserted can’t be read and I get the options to initialise, ignore or eject. When I open disk utility it recognises the hard drive but states it is unformatted (which is not true).
I plugged the hard drive via USB into my Macbook - same message. I tried repairing the disk permissions on my iMac - no difference. I can’t repair any permissions on the external drive as it is all greyed out. Also tried resetting the parameter RAM - no success.
Any suggestions how I could get back my data on the external drive?

Do you hvae the option of testing the drive with another mac? The latest securtiy update didn’t involve any changes related to what you are describing: