This issue is reproducible for me only in Kubuntu (KDE 4.3 - 4.8) on Kubuntu Linux with KDE File Save dialog enabled in LibreOffice (enabled by default). This issue is not reproducible on Windows version of LibreOffice, but must be reproducible on any Linux distributive with installed libreoffice-kde package. Description: If I working with filename, that contain dot (for example "my.filename.ods") and try to save it, extension is not added, and after second "Save as" try last part of filename will be deleted. Normal operation: 1. Create new filename, type anything. 2. Press File > Save, type Name "my_filename", press "Save". File will saved as "my_filename.odt" - all right. Bug reproduce: 1. Create new filename, type anything. 2. Press File > Save, type Name "my.filename", press "Save". File will saved as "my.filename" - extension is missed. 3. Press File > Save As, and look into "Name" field, you will see only "my.odt" (or "my") text instead of "my.filename.odt", press "Save", file will be saved as my.odt. Bug reproduce 2: 1. Create new filename, type anything. 2. Press File > Save, type Name "my.filename", don't press "Save". 3. Change filter from .odt to .doc, you will see that "my.filename" changed to "my.doc" instead of "my.filename.doc. So, this issue adds many problems for working with filenames, that contain dots.
This is a feature of the KDE file dialog (I can reproduce the same problems with Kolourpaint) and it's a question if it is a bug. But given that it's a generic problem with the KDE libraries, you'll need to report the problem there (http://bugs.kde.org).
This has recently been fixed on KDE's side: https://bugs.kde.org/show_bug.cgi?id=431638