After updating to 14.4 and using PlanAhead as the design management tool, the BSP cannot be compiled when in SDK. However, when opening XPS then launching SDK or opening SDK directly, the BSP compilation works just fine; there are no issues.
The issue is that for some unknown reason the setup scripts are not sourced when launching the PlanAhead tool.
There are several solutions, also described in other answer records, for example:
TO C:\Xilinx\14.4\ISE_DS\settings64.bat C:\Xilinx\14.4\ISE_DS\PlanAhead\bin\planAhead.bat