The XMA-tab in FSA works with xmaencode.exe found in XuiTool.
It seems that some wav-files are not converted and if they are they dont work properly under FSD 2.
Here is a workaround:
You need xma2encode.exe (found in the latest SDK I guess). Convert your xma back to wav:
I used Cool Edit Pro 2 but any SoundEditor should work.
Attributes: 44khz, 16bit, stereo.
Use then xma2encode pcmfile /T xmafile
I'll add a checkbox in FSA ( use xma2encode.exe ). It is recommended to use the new encoding executable.