Strange.
I saw this IRL but when I went hunting in GDB it no longer happened.

SVN commit 699102 by okellogg:

slotFileSaveAs(): Apply commit 695283 from trunk which works fine, thanks Sharan.
BUG:146061


 M  +1 -0      ChangeLog  
 M  +0 -9      umbrello/uml.cpp  


--- branches/KDE/3.5/kdesdk/umbrello/ChangeLog #699101:699102
@@ -2,6 +2,7 @@
 
 * Bugs/wishes from http://bugs.kde.org:
 * Cannot move text and label correctly after enabling snap to grid (137041)
+* Umbrello gratuitously appends ".xmi" to the saved file name (146061)
 * Wrong pascal code generation (146676)
 * Crash when linking to undefined xmi.id (146748)
 * End Activity Symbol gets invalid when line thickness is increased (146925)
--- branches/KDE/3.5/kdesdk/umbrello/umbrello/uml.cpp #699101:699102
@@ -734,15 +734,6 @@
         if(url.isEmpty())
             cont = false;
         else {
-            // now check that we have a file extension; standard will be plain xmi
-            QString file = url.path(-1);
-            QFileInfo info(file);
-            ext = info.extension();
-            if (ext != "xmi" && ext != "xmi.tgz" && ext != "xmi.tar.bz2")
-            {
-                url.setFileName(url.fileName() + ".xmi");
-                ext = "xmi";
-            }
             QDir d = url.path(-1);
 
             if(QFile::exists(d.path())) {