Hi y'all

I've previously posted this question on AVForums (http://www.avforums.com/forums/blu-ray-dvd-recorders-media/1575620-nooo-sony-rdr-hxd790-hard-drive-permanently-full-help.html) but thought it worth trying on here too.

I've had my 790 for over 2 years; and it's worked perfectly for me,  altho I only use it to record from external input and burn to DVD as  appropriate.

I haven't done a firmware upgrade in at least 12 months (I can't write the file to CD in the required format - my machne is on 1.15)  and last  optimised about 6 months ago. Having moved about 2 1/2 hours of stuff to  DVD earlier the unit returned to the Hard Drive menu stating that the  Drive was full.
How can it be I think; there was over 30 minutes left (SP) and so I  promptly deleted the other titles I'd just burnt but with no impact.
I started an Optimisation process to try and cure the problem (long shot  given how full the drive had been beforehand), which started and then  bailed out after 15 mins or so. Now if I start to optimise again it  fails immediately....
I've tried to delete a few more files, remove sections from existing files etc which all delete as expected, but its to no avail as it has no effect on the amount of drive available (0h00m)

Beginning to fear the worst for the drive, but as I have other 500  titles left on it (which can all be seen, sorted, played etc) the  process of moving all of the contents to DVD fills me with dread.

So any ideas anyone?
Has anyone experienced anything similar on a Sony x90 machine?

Cheers