D.Opus Freezing when I display the content of all subfolders

I use the display the contents of all sub-folders option to display
all the files in "Very Large" folders , even whole hard drives.

I've never had a problem doing this before. I just had to wait a
while for all the files to be read.

now , it times out. Is there something I can do to optimize D.Opus?
allocate more memory or something similar?

Do you now why all of a sudden I can no longer do what I used to
do all the time?

Try the suggestions in this FAQ for starters. Shout if that doesn't help, but it's probably something along those lines.

Some hard drives (very large ) will display all files in all sub-folders.

But something in some smaller folders/drives is crashing it
like it says in the FAQ.

50% usage on a dual-core until you have to force quit D.Opus.

how can I search for the exact problem causing file(s)?

could it be very long file names?

Work out which files/folders are causing it. That will probably provide clues about likely causes. e.g. If it's a folder full of videos then it's probably a video codec going wrong.

It's unlikely to be long file names.

I read in another post about a special debug version of DOpus.

How can I try using that?

There isn't a special debug version of Opus in general. Every so often one might be made with code to help diagnose very specific issues, or to test new changes before release, but those are one-offs and not generally useful or maintained.

There are debug settings you can turn on in the normal version of Opus, however. Those should be mentioned in the relevant FAQs for the issues they help resolve. (e.g. The Context Menu debug setting is mentioned in the FAQ about diagnosing crashes related to context menus.)