may be you should download MPLABX v2.35 ( from Microchip archives folder http://ww1.microchip.com/downloads/e...-installer.exe ) and NOT the more recent versions ...
just my two cents
If you're NOT interested in using any of the newer devices then you can certainly download and use the old MPLABX 2.35 but if you're buing PBP 3.1 in order to be able to play with the devices it adds support for then you're going to HAVE TO use a new version of MPLABX. Well, it's MPASMX you need but it and the device specific header files comes bundled with MPLABX so....

Personally I've got MPLABX v3.55 installed and it seems to work just fine, compiling and assembling from MicroCodeStudio. As far as setting up PBP as the toolchain INSIDE MPLABX it may be a different story. Charles sent me some instructions the other day, when I bought the 3.1 upgrade but I haven't had time to look into it yet.

/Henrik.