DVD::Rip user problems

Hi

Really confused here.
I have a few iso images that I wish to encode.
I have mounted them, as I cannot see anywhere dvd:rip can connect to
an iso image directly.
Once I read the table of contents,  I attempt to run Transcode - which
fails, telling me I need to rip the dvd first.  OK, but that has
already been done by another piece of software.  So I click the Rip
selected Button on the Storage page and I notice tccat run for a few
seconds, then stop.  I cannot do anything else.  I have to shutdown
dvd:rip and start it again. The only way I can do anything with images
already ripped to my harddrive is set Encode DVD on the fly.
Then I can transcode.
Is this expected bahaviour?

Regards,
Buggy