DVD SP 4.2.2 suddenly not reading discs

Hi all

About a month ago I created a short film with FCP 7 and ran into problems when I tried to create a DVD from DVD Studio Pro as it appeared that my drive on my iMac was malfunctioning. So, I went out and bought a new Apple drive. I had no further problems and through five or six iterations managed to create DVDs until everyone was happy with the final copy.

Fast forward a month and now people would like copies of the DVD. Using the same raw files I open DVD Studio Pro and create a menu, linking a button to the track and check it in Simulate. It works perfectly.

I put in a DVD+R and am told that I've entered in a blank disc, I opt for Ignore.

But when I press of Burn (or Build/Format) I get the message "Please insert acceptable DVD recordable media"

These are the same files, DVDs from the same pack of blank discs and a drive that is only a month old (and recognises the disc anyway) - why am I suddenly having problems burning?

Has anyone had a similar problem?

[DVD Studio Pro is 4.2.2 and OS X is 10.9.5]

I'd ve very grateful for any help!

Thanks

Aidan