Lord C, rongel and Lukey J, I finally managed to reproduce the problem you were having, or at least I think it has same root.
The crashes begin if you make the text in the object selection field too long. I don't know how did you do that, maybe this depends on monitor settings too (different resolution, font sizes, and so on), but what I did was creating a room object and giving it a very long name, something like "AAAAA_BBBBB_CCCCCCC_DDDDDDDD_FFFFFFFFF".
If the line is too long this control begins to wrap it, replacing words with "...", and eventually glitches begin to occur (selection not working, crashes, and so on).