Slow loading viewer, not a good replacement for Explorer

I tried this program for a short time awhile ago and it seemed to work well. Now that I have purchased it, (a newer version?) it won't load the pictures in the viewer unless they are very small. Then when it does try to load a file larger than 10kb, it just hangs without ever loading. Then I have to restart the program and hope I don't click on a picture or file that is too big.
Next problem is that I thought it would replace Explorer completely but when I open a program (CorelDraw x6) then open a file, nothing can be viewed except jpg files or similar.
This is a very strange tech support system too. I hope I get some kind of answer because at this point I am uninstalling DO and going back to sucking crap with win explorer. At least I could see the files I clicked on there.
I want to know if there is an easy fix because I bought this to make things easier. If I have to go searching and testing this and that, I just want my money back. I don't have time to fiddle with crap programs.
Please respond as soon as possible.

Go to Help > About and check the version. Is it 11.18?

While Opus can replace Explorer, it does not replace every window due to limitations set by Windows. Therefore all Open and Save dialog windows is actually Windows Explorer and not Opus. Since CorelDraw is an image program, by default, it probably filters out image files only which is why you only see image files and related files. If you want it to display all other files in that same dialog window, go further right from the File name text field where a dropdown menu should say something like "Image Files" and click on that dropdown menu to change to All files (.). All the files you expect to see should show up. Anyways, this is all Windows Explorer and not related to Opus.

Your other problem related to the loading of images in the viewer, that's pretty odd. Just do a quick test. Start Windows Explorer, Show the preview pane, and select an image that you had issues with before. Does the image show up correctly?