How to reproduce:
1. Open "Accept changes" dialog, resize it to minimum size (the buttons are still visible)
2. Close the dialog
3. Reopen the dialog. The buttons are now invisible until the dialog is resized
I did observe this in 3.3.2, 3.3.4 Beta 2 on Windows and MacOS X; it probably applies to other versions and OSes as well.
[Reproducible] with "LibreOffice 3.4Beta2 – WIN7 Home Premium (64bit) German UI [DEV300m103 (Build:1)]" in Menu 'Edit > Changes > Accept or reject ...'
Not visible in CALC.
It's not a big thing th get invisible buttons back by resizing dialog, but for an unexperienced user it might be really worrying if he wants to decide and has no buttons ...
Grr, this turned out to be very hard, especially as the underlying problem got aggravated in the meantime to cause the list to disappear to a 0 height list in the development version.
I think this is sorted out now with http://cgit.freedesktop.org/libreoffice/libs-core/commit/?id=ed249b94b30655d22400fab0fca0ee8a87cca6a9 and the logical series of patches triggered by it