This one is driving me nuts (though I admit that's a short drive). To see the bug:
Unzip the file.
(If you're using > LV18, I suggest a mass compile.)
Drop "Universal Dialog Box.vi" onto a block diagram.
When the configuration window opens:
Click on the "Entry Field" tab.
For the "Type", select "Text" (or anything other than "none").
For the "Properties" input, select the 1st item "Caption.Text"
Right-click on the Express VI and select Create → All Controls and Indicators.
Double-click the Express VI to reopen the configuration window.
Click on OK (without making any changes).
The wire for EF.Caption.Text will now be broken. I've managed to narrow it down some:
The library is Universal Dialog Box\Support\Universal Dialog Box\Universal Dialog Box.lvlib.
Look in the block diagram of Universal Dialog Box\Support\Universal Dialog Box\Configure.vi.
In the event structure frame  (OK value change) you can see 6 subVIs called in sequence: Apply Title Options.vi, Apply Message Options.vi, Apply Image Options.vi, Apply Audio Options.vi, Apply Entry Field Options.vi. Apply Button Options.vi.
If any of the first 4 (Title, Message, Image, Audio) has it's option set to "No Selection" (the default for all of them), then the "Apply" VI will disconnect the corresponding terminal from the connector pane (as it should). It is at that point that the wire breaks. It's as though it's disconnecting the wrong thing; but I just can't see what's wrong with the code.
"If you weren't supposed to push it, it wouldn't be a button."