I found a similar problem in the old forum, back in 2007, which said it was be fixed in OmniPlan 1.1.1. I am using 3.4.1 and OmniOutliner 4.5.3.
I actually created a mind map using iThoughtsX and saved it as an OPML file. I tried opening it in OP, which seems like it would work, but it didn’t. I then opened the OPML file in OO and saved it as OPML (in case there was something “proprietary”?). It still didn’t work. I saved the OPML file as an OO file. When I opened it in OP, all the parent and children tasks came in “number-wise,” but ever task was blank.
After a few more tries, I noticed that OP said the file was 0 K when I tried to open it. I used OO to save a new copy to a new location: 2 K. I tried opening that. Still blanks.
Am I doing something wrong? I was going to demo the mind map > outline > project plan to our project manager, but now I’ll have to wait for another opportunity to sell Omni. :-(
Thanks for any help!