MCLK msp430F449 doesn't work with XT2 clock source

I'm working with the ms430-449STK2 olimex development kit that IA distributes with its software,

"XT2 = 8Mhz" The problem is that I can't select the XT2 as a clock source for the MCLK In fact I make this instruction:

FLL_CTL1 = (SELS + SELM1) & (~XT2OFF);

and the IAR IDE show me that the right bits are sets, as follows: SELM1 = 1 SELM0 = 0 XT20FF= 0 SELS = 1 However the MCLK works like I had selected the DCOPLUS source.

Like an extra comment, something weird is that I can configure the XT2 a a clock source for SMCLK.