DOpus refuses to honour my jpg viewer settings

Hi,

I'm a long-time user of Directory Opus but it's just started to refuse to open jpg files in my chosen picture viewer (IrfanView). No matter what I do, if I double click a jpg file inside Directory Opus it opens in Directory Opus's internal viewer.

I shift and right click on a jpg file and select open with, then I select "choose default" and select Irfanview, whereupon the file opens in IrfanView - but as soon as I close it and try again Directory Opus uses the internal viewer again!

Windows Explorer opens jpg files OK in Irfan View.

How can I get it to honour my choice please?

Please see: Stop the Opus image viewer from being used by default

Thanks Leo