All is not exactly rosy over here either.

I do get a file not found error, after I successfully compile. Which I notice is slightly different than you. Are you using the new MPLAB X 1.0 (first non beta)?

I can run through with the simulator, I can create hex files that I tested to make sure they really worked. But in my testing of MPLAB X, I can't seem to program the devices directly from MPLAB X when using PBP3. For C, the programmers all work, ICD3, Pickit3. I notice in MPLAB X PBP3, the .cof file is put in \dist\default\production file of the project, but the hex is left in the base file of the project. This is not how it works in MPLAB X C. The hex file and the cof file would be found in the \dist\default\production file for C. So I am wondering if the error I am getting is the rest of MPLAB not finding the hex where it thought it would be. This leads me to wonder if the plugin is set right? This doesn't look like any settings I can select, as far as I can tell. I will ask Charles Leo on the MeLabs site, and pass the answer here when he responds.

Here is a my compiling message:

CLEAN SUCCESSFUL (total time: 101ms)
make -f nbproject/Makefile-default.mk SUBPROJECTS= .build-conf
make[1]: Entering directory `C:/local/new/altimeter.X'
make -f nbproject/Makefile-default.mk dist/default/production/altimeter.X.production.cof
make[2]: Entering directory `C:/local/new/altimeter.X'
gnumkdir -p build/default/production
"C:\PBP3\PBPX.EXE" -ampasmx -k# -os -p12f683 alt-683.pbp
PICBASIC PRO(TM) Compiler 3.0.4.4, (c) 1998, 2011 microEngineering Labs, Inc.
All Rights Reserved.
gnumkdir -p dist/default/production
cp alt-683.COF dist/default/production/altimeter.X.production.cof
rm -f alt-683.COF
make[2]: Leaving directory `C:/local/new/altimeter.X'
make[1]: Leaving directory `C:/local/new/altimeter.X'

BUILD SUCCESSFUL (total time: 3s)
Loading C:/local/new/altimeter.X/dist/default/production/altimeter.X.production.cof...
The program file could not be loaded: File not found.