Problem saving the file after moving worksheets into another
 

I have a 'master' spreadsheet that I would like to add additional tabs to.
I'm not having any problems moving the worksheets into the document but when
I try to save the file its not happening. I have tried renaming the file,
saving to a pen drive but nothing seems to be working. I seem to be able to
save the first worksheet but then reopening and saving additional worksheets
without success. Would anyone have any idea why I am unable to save the
file.....thanks