Hi Andre,
I have been getting this window from time to time. Here are the steps I use to reproduce it.
1. Close Twistpad if opened
2. Open Twistpad
3. Drag and drop a file on Twistpad
4. With the file now opened, I do a control-f to bring up the Find window
5. I type in a term to search for
6. Click More -> Find All
More times than not following these steps brings up the window in the attached image.
After I click OK, everything is fine and I can continue working on the document. If I close the document and then proceed starting at step 3, I do *not* get the pop up window.