SOLVED Problem on Mac adding new time signatures to palette - not there on restart and '"Writing palette file" error

SOLVED ITSELF SOMEHOW...

New to MS on Mac, having worked on PC for some months...

I have created some new time signatures, within the Time Signatures palette. But on restarting MS4.2 they have disappeared.
So, I tried to save the palette through the Time Signature palette menu, "Save palette..." and saving both the original file name 'Time_Signatures' and a new file name, I get a dialogue box error:
'Writing palette file'.... 'failed'.

Where am I going wrong? On PC I successfully added various time signatures to the palette with no problems.

Thanks
Ned