Only beta simulator and beta MPASM assembler for 16F1503
If the support for this part is only showing up as beta in MPLAB X, you should revert back to MPLAB 8 for primary development.

MPLAB 8 can be installed side-by-side with MPLAB X - you can even have overlapping projects on the same source files. In fact, this practice was recommended to me by Microchip when we received training on MPLAB X recently (make sure it works in 8 if there are doubts about X).

MPLAB X is a relatively new product for which legacy support will be improved over time (they focus on the newest parts first and work backwards).