Several players have contacted me with problems with their saved games. Things like items that won't stack or the warrior not being able to equip a shield is among the reported problems. All this boil down to changes I made to the data file that I overlooked when naming the new version 1.8.4. The new version should have been named 1.9.0 to make sure that save game incompatibility would have been detected on startup. I'm afraid I can't revert this if you are playing on an Android device since the Android Market doesn't allow me to revert to an older version. If you use the J2Se or J2ME version it can be downloaded from www.roguelikedevelopment.org/dweller/old/
If you start a new game things should be working as expected though. I'm sorry for the inconvenience this may have caused you. The new 1.9.0 version has been released and is ready for download.