LPG DVD-recorder 'failed to divide' item

Hi guys. Apologies, if required, for any cross-posting of this. I've
an LPG DVB-T HDD/DVD Recorder. Today I recorded an item off-air, and
then wanted to divide it. Normally this is a simple process (except,
perhaps, at the very end of a disc - but this wasn't such a case).
However, when I attempted to do this, a message appeared onscreen
saying, 'Unable to divide disc'. The disc was a Verbatim +RW, and had
already been part used for recording. Any thoughts on why the item
wouldn't divide? (I tried more than once to do so, at different points
in the item.)

Thanks - Ken (in Oz)

Ken