That was a problem in the PBPMPLAB.bat for PBP 2.60 on 64-bit systems.
Windows doesn't like the (x86) in the path.

Add carets before the parenthesis in the .bat file ...

SET MPASMWIN_PATH=C:\Program Files ^(x86^)\Microchip\MPASM Suite

This was fixed in the 2.60A patch.