Arduino 0012 only has booloaders for the ATmega8 and 186. Those will not work with the 328.
In addition, there are source code updates that must be made to some core and libary source to support the 328.
LadyAda, Spiffie, and maybe others have hacked out 328 support for version 0012, and version 0013 I believe will include some 328 support.
-j